Elbows and wrists, tricky to sort and it really is a case of what works for you and experimenting, also be aware of over compensation. I've had ongoing issues having now broken my left elbow twice, left lower arm once and left wrist 3 times, I've also had an operation to remove some bone from the end of the radius to leave a 'floating' joint, ie bone no longer reaches elbow. A complicating factor is that things can be in constant flux as your fitness and strength varies, as well as length and bumpiness of rides, even one pothole strike, in the wrong place at the wrong time, can be enough to set you back. What I've found:-
painkillers are good, never leave home without them and hoard stronger ones, just be aware of side effects and cycling not mixing too well
core and upper body strenth - matters a lot for me and allows me to spread the load far better, my favourite is doing chinups but this isn't always possible, so plenty of situps as the next option
bike setup - tricky as I'm not always sure what is just general wear and tear and what is an ache brought on by the setup needing tweaking - this is the real trial and error bit, I've found that tiny differences in bars can give me real elbow problems
over compensation - I don't actually know but suspect I tried to do too much to soon after the last wrist break, it was only a cracked bone and didn't seem too bad, but I managed to pop something in my right wrist. This happened during the last night ride I did and was evidenced by the appearance of a knobbly protrusion on the inside of the wrist below the pad of my right thumb. This has only returned to normal in the last month or so and was, I believe, a direct result of trying to ride with too much reliance on one side.
maximise ride positions - I've gradually moved over to drop bars, from butterfly bars, and set them up with an additional crosstop brake lever for the front brake only. I have a fairly upright setup anyway, with shallow drops, and this allows me to comfortably brake from the drops, hoods and flats. I did have a pair of crosstops initially but found that just the one was enough for my purposes. It's only really there to allow modulation, from the flats, without having to move hands to hoods or drops. This may not sound like much but I found, on a long ride, I'd often be on the flats having to move a hand/s to brake. My natural way of doing this would be to move the right hand first thus putting the load on the left. The crosstop lever option has greatly reduced the amount of times I need to do this.
padding - again this is personal but I've gone to using less padded mitts/gloves and I have foam tubing underneath the bar tape all round. I tried some of the gel strips etc but found the foam tubing easier and gave results I preferred. It does make for much chunkier grips though so size of hands would be a big influence on this.
brake levers - no reason you couldn't reverse front and rear brakes to let the left hand take the strain
grip strengthening - I have those squeezy spring loaded hand grips from my golfing days and, just like improving core strength, they really do help improve grip strength. You could also consider something like a Powerball which would work on wrists and forearms more.
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