Windows have to be painted on all sides or unfinished portions will be visible through the "glass". Paint them all ahead of installation and be ready to wait the drying time. That way when you're ready to install them, it's much like a breeze.
I have a trick for painting multiple windows parts at once, which is:
1. Lay out a piece of parchment paper.
2. Have a cup of water handy and a damp towel.
3. Squeeze out the paint onto a dish. If you're using multiple colors, squeeze each into separate dishes.
4. After wood preparation, like sanding, categorize them. Ex: all trim together, all sills together. Make sure you separate interior from exterior.
5. Choose a color for each piece and paint. Ex: I want green window sills so I take all of the sills and paint them one after the other.
6. Paint one side and section at a time. Lay on parchment paper to dry and start a new piece.
7. Repeat for all pieces until complete.
This method keeps you working and saves time. It also assures you the paint has dried with minimal paint defects and that you do not accidentally paint the wrong piece a wrong color.
I finished painting all of the tower windows, attic windows and doors today.
I used alternate schemes for the kitchen and front doors.
I will be gluing versus hinging the doors. Knobs go in later because I am using a gold jewelry bead. If you are using real miniature knobs, you will need to apply your knobs before installing your doors because they have to be tapped in place.
Trims will be painted white.
After everything is dry, bag all of the pieces to avoid loss and mix up. The colors remind you of what each piece is. Label bags to know what's in them.