JimL wrote:
I need some suggestions on how to join crown molding and door molding
and floor molding.
I don't own a fancy tool that will cut biscuits or any such thing.
But when I join sections, I'd like the joint to disappear when
painted.

Since you're painting it you have lots of options. If you truly want
the joint to be seamless, then you're looking at gluing the joint
(polyurethane or epoxy) and then sanding and/or filling. Prime the
trim and fine tune before finish painting.

R