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.

http://www.painttalk.com/f6/painting-6-panel-door-1407/

I've done it both ways and always use a small foam roller. I prefer doing it when they're down, because I like being able to remove all the brass. Some folks prefer a brushed look on doors, but I like smooth. I cheat with the roller by pressing down in the nooks and crannies to get the paint in them and then roll over it to get a smooth finish. Sometimes I have to feather the nooks and crannies with a brush as fnm said, but not too often.

The advantage to painting while the door's still up is you can do both sides at the same time. The disadvantage is you have to cut in around the hinges and you have to worry more about drips and drops. The disadvantage to painting them down is you have to do one side at a time, so it's going to take longer, and you increase the chance that somethings going to fall on the finish while it's wet.

As you mentioned above, I think use brush to paint a 6 panel door. Brush gives proper style if running with the wood grains. I would also like to suggest you that before start painting the doors you should lay down the doors to reduce drip and improve paint.

Here is a link that might be useful: painting services