John Willis wrote:

In my original reply to the original poster, I suggested, for a nice,
smooth finish, three coats of primer, with sanding and cleaning in
between, and two finish coats, with suitable sanding and cleaning in
between. This process fills imperfections in the surface with the
primer and give good coverage with two finish coats. Of course, more
may be applied if one desires...

I'm sure you get good results, John, but it just seems to me that
you're using a product to do something it wasn't designed to do.
Primer has very little body and build up. Essentially you're using
something closer to water than paint to fill imperfections. If the
surface needs to be filled, use a filler and sand it prior to priming.
Otherwise finish paint has far better filling capabilities than primer.

I'd imagine that part of the reason you do what you do is the longer
drying time of oil paint. The oil primer would dry more quickly than
oil finish paint, so in that respect you save some time. Still a lot
longer time in between coats than with latex, but to each his own.

R