For paneled doors, remove all hardware or cover it with masking tape. (If some paint inadvertently gets on metal parts, wipe it up immediately with a soft cloth.) Paint the panels, working from top to bottom. For each panel, paint the molding first followed by the interior. Finally, paint the rest of the doorl finishing with the outer edges. If the door swings out, paint the hinged edge; if the door swings in, paint the lockside edge.
If you just bought a manual miter box, a simple modification will extend its useful service life. Insert and fasten a piece of 1x stock to the inside bottom of the box. The saw blade will then cut into the false bottom, without damaging the miter box itself. Occasionally move the wood back and forth, or turn it over, to spread out the wear. When badly cut up, just replace the piece.