Have you used the Dupli-color SEALER?? It is not the same as the Primer. Both can be bought in gray......the sealer to me is like a scale primer. I keep Dupli-color primers on hand too in all the colors they offer. But I use more 'sealer' than anything.
I can get the Dupli-color at our Magic Mart cheap....and I don't like change....so when something works...I just tend to stay with it. Whatever works for each is good!