The BIN ( AKA white shellac) will stick to anything, no need to sand, but I’d advise cleaning with a detergent or TSP solution to remove any dirt, and scuff-sanding to remove any defects in the existing paint. BIN dries fast, so flow a lite coat on with a china bristle brush and watch for runs/drips. Avoid going back and re-brushing after about a minute has elapsed; doing so will drag the partially dry BIN and put brush marks in the coat. BIN is available in aerosol cans, so if you are only doing a door jamb or two, that may save time and create a smooth foundation for the topcoat. I’ve found the aerosol cans put out a strong spray, so it’s easy to flow too much on, causing runs, so do light dusting passes until you get the hang of it. After it dries in 30 minutes go back and lightly sand out any defects; go easy, this stuff clogs sandpaper easily; I like to use the soft sanding sponges and suck out the debris with a vacuum after a few strokes. Your brushes and tools clean up fast with a dunk in denatured alcohol to get out the bulk of the stuff in the brush, then dunk in janatorial strength ammonia (I pour some in a pint size mixing cup, then swish the brush around in there) then rinse in soapy water, and finally rinse with water. If done carefully, the final paint coats come out glass smooth. Good luck!
