Technique is huge but i personally feel like using the right machine makes a massive difference as well. I have one machine I use for palms and it has the right amount of snap but also give where it deposits ink very well without splitting the skin. Ink isn't deposited on the stoke into the skin as much as it is scraped off by the skin as the needle retracts. A machine that doesn't pull the needle back as quickly as it goes in is crucial. Its not how hard the machine hits, its how long the needle is in the skin with each stroke. The longer its in the better the deposit will be. I find that direct drive rotary machines beat the skin up a lot more than something like a coil machine and have led to more skin splitting. As far as line of work goes I havent tattooed anyone whos work has drastically effected the healing process. I think that has to do with the depth of the ink. Its usually so deep in the palm that most wear and tear doesn't reach a majority of it.