I've been using shellac to seal pine knots and I've been happy with the
results in that the knot doesn't bleed through. The problem I have is that
I usually end up painting the project with white paint which doesn't cover
the shellaced spots very well. I have to put on at three coats of paint to
cover it and even then, it still doesn't look very good. Before anyone
suggests I switch to a different type of wood, I use pine because it's cheap
and I don't mind covering it with paint. I'm not a big fan of using a
hardwood to just cover it up with paint.

Does anyone else use something besides shellac to seal the knots that works
well when painted? I know Zinser makes a primer that includes shellac and
I've used it before but after a year or so, the knots still bleed through.

My method once sanding is complete is to put the shellac on the knots, sand
lightly with 220 grit, then apply latex primer, sand again lightly with 220
grit, then apply latex paint.

Thanks in advance.