lessons learned while trying to ink with a tablet:
1) use a hard round pen with no pen pressure or dynamics.
2) slow and steady wins the race. patience is a virtue.
3) like inking with pen and paper, spin the canvas around so that you don't have to turn your wrist at an awkward angle. This was actually harder to do if you didn't stick to 90° turns, as the canvas got bigger and bigger and bigger if you used the arbitrary rotation command... I found that creating an action for 5° turn, 1° turn helped to quicken the process of turning it. And cropping the image when it got too big. Pain in the neck? YES... but the benifit was that the inking was easier and smoother than trying to ink a line that I had to turn my wrist a certain way which would cause a mistake or less than desirable look. Also, when rotating, it's easier to ink lines that are generally in the same direction while you have it rotated is better than having to rotate multiple times to that same degree just to ink one line here.. and one line there...

Hope that helps... actually.. I hope that made sense....

This was in PS, btw... I don't know GIMPS commands... sorry.