"masonite" is the generic name for tempered-hardboard, a wood particle and glue panel made with heat and compression by many manufacturers, and the material is still used by the Masonite Int. Corp. as the facing of some of its molded composite panel doors but other door manufacturers often use a molded wood fiber board facing (MDF) which is superior in many ways. The frame of a molded composite door at its perimeter edge. The core can be solid particle board (SC) or hollow with mineral wool/honeycomb/corrugated cardboard (HC). I have never specified a composite molded door but if I did I would avoid a hardboard or particleboard facing and use an MDF facing with a solid core and a smooth rather than textured finish. IMHO the best painted paneled doors are cut from one piece of MDF with a router and Jeld Wen and Bolection offer better choices in all door types than Masonite. Here is a link that might be useful: Bolection

An MDF door will dent easier than a non-MDF solid core door. Solid core doors feel more substantial when you open/close and offer better sound dampening. They are more expensive, but well worth it, imo. We wanted solid wood doors. Had our window guy bring a sample door over from ATL. Although pretty, it was on the thin side. When I knocked on it, it just had a bad feel to it. Felt cheap. So definitely see a sample, because I would have been highly disappointed with these doors in our home. Ended up calling our local lumber yard we were getting the lumber from, and they had the perfect solid wood door that was thicker. It was even less than the ATL door - a bonus, and not the deciding factor. Our doors are stained, and we did have a few issues with movement after installation (with the panels), but I simply went around with the stain can and a rag about 6 months after we moved in. Only one door panel split. Our house is 6K so we have a lot of doors.

We are going to building soon and we have been buying old doors for our house. I want everyone bedroom to have a different door. We are going for an antique farmhouse. It's going to be very different and I don't care. As long as you have the doors before you start the build it'll work fine. We are keeping the old doorknobs and everything. I can picture it all in my head. I say as long as you like it, do it.

Molded door so no true floating panels, therefor caulking will not be necessary. I would select the same paint/finish for the doors as used for the jamb and trim. That is personal, for appearance, not a necessity. I use a semi-gloss enamel. Not familiar with the paint you reference. Make certain the surfaces are clean and free of any oil. Wash with Dirtex, or similar, if necessary. You might find that a foam roller will give you a smooth finish but you'll still need a brush for the 6-panel inside edges and the edges of the door itself. A good quality paint will self-level, just don't rework following application. Yes, personally I prefer to paint doors flat, resting on horses as I have a better chance of eliminating runs. I do two light coats a day apart, flip the door and do the reverse side. I remove the hinges and knobs/mechanism too - less trimming. I'm sure one of the pros can offer some techniques but I don't paint doors often so the above has served me well. Hope this helps, enjoy the new bathroom.