I use 3/4 for just about everything. Use 1/2 for back rolling ceilings.
Not sure if I am committing some painter's code of honor here but I had 10 interior panel doors to paint; decorator white (BM) and tried one of those 6" foam rollers. I did brush the inner panels but rolled everything else; came out very nice! With flotral added, it looks like glass now. I averaged 12 minutes per door side first coat. Your thoughts??
You should be able to brush out a door and jamb in less then 20 minutes. Just my thoughts