If I am using Tamco high build, reduced 4:1:1 for a sealer... do I need to sand that (the sealer) before shooting my base coat?

Not needed unless you have to sand out texture or any imperfections, dirt, etc.

Does Tamco primer when reduced as a sealer have zero dieback like a dedicated urethane sealer? Just because a primer that can be used as a sealer does not mean it will perform like a product formulated for a specific purpose. Many DTM's state they have multi purpose use, but they fail to state the drawbacks. Like the dieback encountered when using epoxy reduced as a sealer.

Scott, he asked about sanding...but to your point no 2K product that adds reducer to the mix is going to be totally immune to die-back.

Need to let it flash off real good, let all those solvents out-gas well -- then proceed. Guys DIYing at home typically will not stock a dedicated sealer and will reduce 2K primer or epoxy...I've done it many times and never had die back, probably because I'm so slow I'd go broke if I had to work in a shop.

Also if the car is in primer already then obviously no need to add sealer on top of that, just go to base.

Thanks for pointing this out, it's a good thing to be aware of.

chris wrote:...I've done it many times and never had die back, probably because I'm so slow I'd go broke if I had to work in a shop.

Haha, same here...

I have used the Tamco gray 2K and the black DTM, both as a sealer. No problems, even when reducing up to 20% (not recommended). I had some mixed spots of filler, sanded 2K and some sanded factory paint that I was going over. I usually reduce it to the viscosity of milk.