In reply to Removed Userherblai:
If I'm wearing my b3 boots when its warm then I often put some zinc oxide tape over my heels and use plenty of talc to keep my feet dry, stops me getting any blisters.
Try different methods of lacing too. I always tie some extra reef knots so I can get the laces really tight over my ankle (see
http://andy-kirkpatrick.com/articles/view/advanced_bootlace_techniques) My partner laces the last two sets of hooks in reverse order (might not make sense without a picture) and swears by it, but it's never worked well for me.
Though, as people have already said, you might just need to toughen your feet up.
If you're going to wear B3s regularly then it's probably best to invest in a pair of your own. They'll break in to your feet and also you can get used to walking in them before you go on any trips.