I assume the pain is in the fretting hands and the blisters on the plucking hands?
The blister is there because you have to much pressure on the friction you create when plucking.
So either lighten up the touch or let the blister develop into a callus of sorts, hard skin, and the proble is solved.
Or do as many players do uses super glues on the tips to protect them. But it must be a, Butyl Cyanoacrylate, based super glue, one used to bond skin. Check the formula on the packet, it should state which one it is (super glues have two basic formulas, Cyanoacrylate and Butyl cyanoacrylate).
Search for what the brand name is for your area, there are many brands to choose from, I use the one with a brush.
I just paint a thin coat on, blow it dry, then repeat till I get the thickness I want.
It soon wears off, but it will highlight the idea that, if my playing is removing that much glue then I am indeed playing to hard.
Pain is easy to check and relieve because you are playing with to much pressure, that is the number one reason for that pain you experience. Constant use of to much pressure if it develops pain is normally ignored under the idea of "no pain no gain" which is a totally false way to deal with any bass playing related pain....playing bass should be pain free.
Before you play you should warm up and stretch the hands and forearms, chech the link below for the basics in stretches.
These stretches are the more common for the muscle groups using in playing. Pay attention to the thumb stretch and the finger spreads section as they apply to your problem http://www.youtube.com/watch?v=C_FZichHw1w&sns=em
First off relax that grip and rest the thumb against the neck, do not hold the neck in any way. It may look like a hold, but it is not.
If I asked you to hold on to something with the amount of pressure you use on the neck of a bass you would drop it...therefore you were not holding it, you just touched it.
See the link below for more info on that subject.
If any of this raises any questions, post them here or PM me and if I can answer them I will.
That pesky thumb http://www.youtube.com/watch?v=OM-rk...eature=related
That pesky thumb pt.2 http://www.youtube.com/watch?v=WREN2...ture=autoshare