Ron, Stuart is right, just change your habits a little tiny bit, mix smaller quanities. That is all it will take, mix smaller quanities. You can mix up 8 oz and spray that little job and then clean the gun with some lacquer thinner, I did that every day for years when I had a small one man body shop.
The only other way that makes any sense are that some etch primers can be left in the gun for a number of days. So, even though they are themselves lacquer based, they have acid and will bite much better. So you could etch prime them and then after having a number of spots or pieces you could run a red scuff pad over them and urethane prime them.
But honestly, just mix less and spray them with epoxy to protect them.
Brian
