maybe a little stressful on the live stock, I've not painted a tank yet myself but I've read that most people end up doing like 2-3 coats of paint so you should factor that in, you could possibly speed up drying time with a hairdryer, when I picked up my saltwater set up from CL I had the livestock in a bucket with an air stone for a couple of hours an they were fine, so maybe put a heater in the cooler and something to help aerate or circulate the water and it should be ok as long as you keep a close eye on them