DES
Well-Known Member
To each his own, I suppose, but generally fill first, sand to level, then prime. The primer will fill in any sanding scratches or minor surface defects that are left after sanding the filler, and leave a uniform ground coat for subsequent paint. Very little to no sanding required on the primer at that point. But if you prime, then fill, you will probably have to prime it again before painting, as the primer and filler have different colors and porosity that will telegraph into the top coats.Wouldn't it be best to spray on primer first then next apply the putty?
Also, with the smear and wipe method, the solvent based filler putty will soften and lift a lacquer based primer, leaving you a mess and more sanding once it all dried.