We are a high end residential cabinet shop. We do all face frame construction. I have heard a lot about people using pre finished interiors. I think that it sounds great other than I can not figure out a way to easily mask off the inside of the cabinet so that the face frame and and exposed ends can be painted. We currently paint the inside of all cabinets or if they are stained the inside just gets clear. How are most people doing this?

One option for a high end shop is to use a piece of cardboard to cover the insides of the cabinet. Cut it about 1/8 smaller than the exact measurement as this will make it easier to insert and or remove. Drill a hole in the middle of the cardboard....it acts as a finger hole and facilitates easier removal. Put a small piece of tape over the hole prior to spraying.

Before inserting the cardboard, run a 3/4 inch of Blue Tape around the inside of the cabinet, then set your cardboard in place and run some tape around the cardboard to hold it in place.

The cardboard that covers plywood can be used, and it can be used over and over.

What Robert said. The taping is somewhat laborious, but less than painting the cabinet interior. Works for low end shops too.

I'll wrap tape around the inside of the opening and then put a pc of cardboard in there. I make them fit snug. Then as much tape as you want to hold it in.

Lately I've changed tactics and got the pre taped masking plastic. Comes in 2' (4', 8' and 99") lengths on a 90' roll. Just mask the inside of the cabinet. Sometimes the cardboard is quicker, sometimes the masking plastic is. I use it to mask off the interiors of my Euro boxes. I leave the edge of the edgebanding exposed so it gets painted also. Nice clean look with no gaps at the joints like you get with pre finished edgebanding.

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Here's my latest cabinet with the masking plastic.

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All of the above except we cut the cardboard 1/16" oversize to fit snug and stay in place. Use 2" tape and you can push the cardboard in a little to prevent bounceback on the inside edge of the face frames.
I actually have a razor knife attachment for our CNC that nests and cuts out all the cardboard pieces.

I use 1/4"plywood instead of cardboard. Over the years I have used cover sheets & scrap plywood and cut them into various sizes that will fit into the cabinet boxes.I put a piece of 2"tape on the bottom only just inside of face frame. I use 3/4"screws and fasten the plywood to the back of the frame.If the opening is wider than my plywood, I will use 2 pieces and let them overlap in the middle. I tried cardboard at first but this seems faster and I don't have the problem of the tape turning loose and the cardboard falling out. I have been using the same plywood pieces for the past 10 years.

Find a local printer. Have him order you a bundle of 90 basis chip board. That is 90 pieces, 22 1/2 x 34 1/2". Have printer cut it to inside cabinet dimension, and cut part of bundle to vertical height. The chipboard is very absorbent, and can be resused many times. 5 minutes a box to install and tape.

We do more custom sizes than standard. Cutting cardboard is slow and you need lots of cardboard. We use masking paper and a razor blade. Same masking tape method.

Once you go prefinished its hard to go back.

I do as above on edge banded cabinets, but with Face Frames I spray the frame separately then attach.

while I do most of my frames separate now, I have done the tape and paper method for years. It is faster than cardboard ect... Just look at how the auto painters do it with masking dispensers. With a little practice you can have one taped down in 5+ minutes

Just thought I'd throw this out there as a different angle to consider. We have lots of customers who use the Tenso connectors from Lamello to attach face frames done in one finish/solid lacquer/etc. onto prefinished cabinet boxes. The connectors are self-aligning and self-clamping. Allows you to flat-finish all parts and assemble afterwards. Your finishers will thank you!
I'm the Lamello product manager here at Colonial Saw and also a former shop owner, so I can help you learn more about it if you're interested.

Tenso-P-14