Painting - Painting molding

In general is it preferable to prime/paint molding prior to putting it down or better to prime & paint after you have placed it?

Same question applies to new doors - Hang first then paint & prime or vice versa.

Probably not a major difference , just curious what the "pros" would do. Thanks

Most door manufacturers recommend that immediately after fitting, cutting for closures, weatherstrip and/or threshold and before hanging any interior or exterior door on the job, the entire door including the top and bottom edges must receive two coats of paint, varnish, or sealer to prevent undue absorption of moisture.

Priming trim pieces prior to installation will save you time. I have seen factory primed trim. After installation, caulk any gaps between wall and molding and then paint.

I agree that it is easier to prime and paint molding, install it , then touch it up.

That is what I do. Have been working on mine for a year now. Replaced all doors and mill work. When the weather gets bad I will finish up. On new doors, I would remove the hinge pins and tape the hinges for painting. Thought removing the hinges from the doors with my cool power screw driver was the way to go. Had to work to adjust them to close after I did that.