It's going to depend on exactly the nature of the drift. I was having a similar problem recently where my pen would start by being supported by the pad of my thumb, but it would slowly slip down my thumb until it reached about 2/3 down the length of my thumb. At this point the game would basically instantly become unplayable and I'd die. I changed my grip so that I was leaning my hand forward with the pen at an ~45 degree angle from the tablet, and this made it so that the pen could not slip as easily (this is probably extremely hard to visualize, especially without a detailed description of my grip to begin with, but my point is just that there is no solution that fixes every grip issue).