The only engine I ever got blisters from was my first into the hobby... Stupid manual... It should say on the front "READ THIS YOU MORON!!!!". After killing about 8 normal c-batteries in my glow heater and tearing the skin off 4 of my fingers, I gave up... then I read the manual.
OOOOhhhhhhhhhhhhh... You have to PRIME the engine by plugging the exhaust thing!!!
After that, no more blisters. Then I learned that there's a break in period... I really hosed that first engine really good.
Now I'm on engine number 10 or 12, vehicle 5 or 6 and the only problems I have are finding times to run.
After installing the cool little MGT primer bulb on my buggy and my savage, it only takes 2-3 pulls (once the bulb has been pumped to fill the line) to get them started.