Here's a suggestion that sounds odd but which works WONDERS. I learned this a few years back when it was january and the local store was selling off Xball Gold for $20 a case...I guess people were buying it and the shells were so thin it was breaking and they were then returning it.
Anyway, do this:
1. Get a case of (your choice) brand paint in advance
2. On the day you play, open the bags and leave them on the counter while you take a hot shower...really get that steam going
3. When done, run your hand under warm water, shake it once or twice, then swirl it through each open bag
4. Close the bags back up with a zip tie
5. Nestle the bags in your field bag with a Nalgene bottle full of warm water
Using this technique I have shot the thinnest tournament grade paint in sub-freezing weather with ZERO breaks. This is SO much fun when everyone else is just shooting thick shelled paint and cannot get breaks just bounces...
Seriously, TRY IT!