etch primer

[les]

Should etch primer be rubbed down before cellulose primer/filler is applied, or when dry primed before rubbing down?

[chickenjohn]

Should etch primer be rubbed down before cellulose primer/filler is applied, or when dry primed before rubbing down?

Not necessary, unless you have some spots and runs from the etch primer.

What I do after any welding repairs are complete is etch prime the whole panel, then fill any areas that need a skim, sand the filler smooth, etch any bare steel again, fill and sand etc till the panel is completely smooth. Then dust an etch primer over the whole panel, let it dry and apply the filler primer layers- 3 or 4, then let dry, guide coat, flat again and finally prime again.

So no, all you need is a thin layer or a dusting of etch primer to bite into bare metal and filler and provide a substrate to which the filler primer layers will stick. It is these filler primer coats that will be sanded.

[les]

Thanks John, will carry on as suggested.