There could well be setup or technical issues partly responsible, but some folks (myself included) just seem prone to them. I sometimes found that changing string brand or tensions could bring one on (usually 2nd finger) regardless of how regularly I was gigging etc @ the time. It's down to about 1 a year now, thankfully. Anyway, here's my personal blister ritual :-
Pop the blister with either a pin or nail-clippers towards the outside (left side with palm down) of your finger - this means that the cut or hole should not be opened further by pizz action - and drain.
Apply surgical spirit to clean & harden the area as often as you can.
Try not to play for a couple of days.
When you have to play again use some kind of liquid bandage/new skin over the area. I use Comspeed Liquid Bandage, which has an integral painkiller as well. It's quick to use and can be re-applied between sets!
Hopefully by the time the blistered part (which may now in fact resemble a callous) gets pizzed off

the skin underneath will be rugged enough to take anything spiro reds etc can throw at it & callous up nicely.
This method has got me through the last few blisters that I've had without too much discomfort, but we're all different, so...