I'll echo the ditto to the excellent advice that others have already posted. In addition, drop bars give you lots of options for hand/arm positioning so, if you can get in the habit of changing positions fairly often, that might help also. Elbows shouldn't be locked, keep them a bit relaxed and don't use your arms/hands to lean heavily onto your bars, as arms aren't supposed to be the weight-bearing limbs in cycling; they're more for balance and to easily absorb road vibrations (again, only if they're not rigid and locked, with you leaning your full upper body weight into them). On long rides, I find it helpful to not only change hand position, but to shake them a bit too (just have to be careful to not wave and shake if riders are behind you and think that you're flagging a road hazard to them). That loosens them up and I open/close, make fists, etc. as I'm reaching for snacks or water bottle, etc. Lots of stretches that you can do while riding, that'll help in between rest stops...hang in there!
Mary