All of my indoor enclosures are painted. Many of them have been in service for over 20 years and most have only been repainted once in that time. I use a good quality semi gloss alkyd enamel latex paint. Primer and then two coats of finish. Latex paint is water based so does not give of any harmful vapors. The enamel provides a hard durable finish and a semi gloss or gloss makes it easy to wipe clean.
I don't put animals in the enclosure for about three days allowing the paint time to fully cure.
It depends on if your tort will claw at the paint or if it will chip. The paint is toxic to consume, but your torts may not be at risk depending on where you are painting. I used linoleum on the walls and floor of mine, then painted the ceiling and the outside.
None of my tortoises have ever clawed any paint off. Latex doesn't chalk or flake off like older lead and oil based paints do. If you apply latex and it's coming off, you haven't prepared the surface correctly for the paint to adhere.
I just painted Dale's enclosure....two coats primer and two coats paint. I just let it dry outside for a few days until it didn't smell anymore. Of course for Dale we had to line it with plastic.