I am retired computer guy and rookie car painter. I love this forum and need some advice.

I am restoring a '69 Camaro in my garage, after bodywork, I started spraying SEM DTM-50121 primer filler (epoxy blend) because it said, I could spray on as a filler, or reduce and use as a surfacer/sealer. As a Sealer 4-1-2, it sprayed great over hinges and braces. As a Surfacer 4-1-1, it seemed thick and left an orange-peel bumpy effect on my fenders/qtrs. As a Filler 4-1, over my hood and doors it was very thick and difficult to spray, I had to remove my gun filter and even reduce the remaining to finish that gallon of primer. I ran out of SEM, and my local vendor recommended the house brand SMART DTM-4400. The salesman did not recommend reducing, and said it was sprayable. It was impossible for me to spray using my regular gun with 1.7 tip @ 20psi. I ended up rolling 2-3 coats on the remaining panels and body shell. The salesman gave no real help.

Q1) Should I be able to spray most epoxy DTM filler? What am I doing wrong? Is there a special gun for this primer filler? How do you apply DTM epoxy filler?

Q2) Both DTM products were listed as GREY, the SEM-DTM was almost white and the SMART-DTM is almost black. My basecoat is Toyota Ultrasonic Blue Pearl. Do all my panels need to be primed with the same color or will the blue look different over white primer on fender to dark primer on doors, etc.?

Q3) While sanding my primer filler (bumpy), I sanded through to bare metal in a couple areas. It is smooth, but the biggest spot is golf ball size and smallest is a few shiny scratches. Do I need to spray a sealer and re-sand over those spots, or shot the entire car?

Q4) with Q2 & Q3 in mind, what product from your storefront do you recommend?

I would be happy to post pics or answer questions.
Any comments, personal experiences or suggestions are appreciated.

The technical data sheet gives information concerning mixing rations, gun tip sizes and application.
https://www.semproducts.com/manage/html ... r_0419.pdf

The Tamco DTM primer sold on this site in the Store Front would be a better choice than the generic "house brand" the local paint store is selling you.

I like to cover all bare metal with black epoxy primer first. Then use a gray build primer so that it is easy to see when I am close to removing all of the build primer.

Generally, you will spray 3 coats of primer filler and let it cure. Apply a guide coat and then block sand with a coarse grit paper to remove the guide coat thereby getting the panels straight. (See Sticky Post at top of this forum)

This process may be repeated a couple of times using a finer grit sandpaper each time until you can remove all the guide coat without seeing metal.

DTM primers don't need epoxy primer under them so I rarely use them since to me epoxy primer on bare metal is critical when restoring classic cars.

The primers can be reduced as the technical data sheet will show for the different applications. Generally, a urethane reducer is used to thin the paint until it sprays as desired.

You didn't say what spray gun you are using that has a 1.7 tip, thus it is hard to know if your 20 psi at the gun is correct.

Thanks for the quick response 68 Coronet R/T
Yes, That's the SEM TDS sheet I've been using, I even called SEM tech support, w/no help.
The SMART4400 DTM TDS sheet is similar, without the reducer info or tech support line, http://www.finishmaster.com/prod/assets/TDS4400_1.pdf

The gun I'm using is an HVLP H827W spray gun. The TDS for both products say 1.7 tip and 8-10psi should work fine. I tried that but SEM worked slightly better at 20psi than 10psi. SMART would not spray out, just clogged. It seemed fluid enough to spray, very frustrating.
I was hoping to hear someone talk real-life exp like, "Yes, I do it all the time" or "No I have to roll it on" or "Try this trick...."

My dad has an old SHARPE model 50 syphon feed spray gun that I could try next time.
It has a 22 on the tip and looks slightly bigger. I'm not sure if syphon feed cups are better or worse than HVLP with DTM epoxy primer filler.

I am an amateur like you. I think your gun tip is too small for your primer. I would recommend as a cheap fix the Harbor Freight purple gun. Lots of people use it for primer and at $10-15 it is very affordable. Be sure to clean it thoroughly before first use.

Your gun is more appropriate for base and clear coats which are much thinner than primer.

I agree Tamco is a good brand and I use their DTM primer. Even with the purple gun I like to add 5-10% reducer to thin the primer slightly so it flies better. I use 30-40 psi and it goes on great.

Ghostbuster wrote:Thanks for the quick response 68 Coronet R/T
Yes, That's the SEM TDS sheet I've been using, I even called SEM tech support, w/no help.
The SMART4400 DTM TDS sheet is similar, without the reducer info or tech support line, http://www.finishmaster.com/prod/assets/TDS4400_1.pdf

The gun I'm using is an HVLP H827W spray gun. The TDS for both products say 1.7 tip and 8-10psi should work fine. I tried that but SEM worked slightly better at 20psi than 10psi. SMART would not spray out, just clogged. It seemed fluid enough to spray, very frustrating.
I was hoping to hear someone talk real-life exp like, "Yes, I do it all the time" or "No I have to roll it on" or "Try this trick...."

My dad has an old SHARPE model 50 syphon feed spray gun that I could try next time.
It has a 22 on the tip and looks slightly bigger. I'm not sure if syphon feed cups are better or worse than HVLP with DTM epoxy primer filler.

The 8-10 psi for the HVLP is "at the cap" pressure. The inlet pressure will be higher than that and is measured with the trigger pulled full open.

This from the specs sheet: "Optimal working pressure: max3bar/45psi"
So you should double your PSI setting at the gun.

Also if it has a plastic screen inside the cup, remove it and toss it in the trash. You should be screening the paint when filling the cup so no need for it.