I bloody hate my boobs! (Well at the moment anyway!)
Am usually a 34G, went up to a 40GG at about 20 weeks and got measured today as a 40HH at 32 weeks. (Ribs have expanded MASSIVELY, not just weight gain).
I've found that spraying deoderant (the anti-persprint 'Sure' that I put under my arms) stops them sweating and therefore rubbing! Not sure how safe it is, but I guess if i'm not breastfeeding its only the skin, not anywhere near my nipples!
When I went to M&S at 20 weeks I got told to stop wearing my underwired bra and they fitted me with a maternity bra with breastfeeding cup things. Felt weird at first not wearing wire! But I know you're not supposed to so I got used to it. After i'd washed them once the they really slacked and made me feel so saggy and gross. They didn't really 'lift and seperate' as my mum said and felt more like a crop top. When I went back today, I told them the issue and they said as long as I don't need breastfeeding cups, then a normal non-wired is fine. Am now wearing one that feels amazing! It's got thicker straps than before and three clips on the back. Really pulls them up off my chest and has so far minimized rubbing!
Wearing no bra would worsen the problem in my opinion anyway, I usually wear a bra to bed because my boobs are so heavy on my chest.
After all that :D As a fellow big boobed girl, I recomend after using savlon to heal any broken skin. deoderant daily to stop sweating and therefore rubbing (you may not even realise you're sweating) and a good fitting bra! If you find the maternity ones aren't supportive enough, then you'll have to sacrifice the breastfeeding cups for a normal bra for now, just to keep them high up!