Everybody has a different idea, from baby-wipes on up. I've seen most people use ordinary Windex or other window washing solution, and a roll of paper towels. The windex thins out the oil and makes it easier to wipe off with paper towels.

No need to go nuts on this. As part of you post flight, you might also want to run up your engine at full throttle and pull the fuel tubing off the carb to run the engine dry. Then, add a few drops of after-run oil down the carb intake and into the glow plug hole. Running the fuel out of the engine will prevent the bearings from rusting (the fuel is hydroscopic, i.e., it attracts moisture). The after-run oil prevents that.

Bob