I am not a medical professional so don’t take this as medical advice but what I used to do in my college playing days to rebuild calluses quickly was to take a long hot shower until my fingers got wrinkly and soft, and then went and played as soon as I got out. That would do it for me quicker than just playing. Bass calluses are different, guitar strings cut so their calluses tend to be hard, bass strings are more abrasive than cutting so our calluses tend to be more leathery, usually.
As far as blisters, and remember I’m a random internet guy not a medical professional, what I was taught to do was sterilize a needle, and poke it on the trailing side, not the side that contacts the string first, but the back side where the string will release from your finger. The reason is that you don’t want your continued playing to rip it. So, after you poke it and drain it, leave it to dry as long as you can. It will dry and get hard while the the soft injured skin underneath heals. Hopefully it will stay there until the underneath is healed. Once you get to that point get some cuticle nippers and clip off the old hard stuff as close to the edge as you can. Use a nail file to clean up the edges after clipping. That did the trick for me. If you need it, the fabric band aids or fabric hockey/athletic tape will provide some good protection if that fails or you clip into fresh skin getting to the edges. Good luck.
Also, those were tips from when I was playing 12+ hours a day and my hands were taking a beating, it was overuse not non-use. If your skin isn’t hard enough to tolerate that level of playing maybe your tendons and muscles and ligaments and stuff aren’t ready either and could use a slower build up to increased playing time. Be smart, make good choices and work up your whole system together. Carpal tunnel syndrome is a lot worse than some blisters.