What is the best tool to do waterslide decals. I’ve been using a ballpoint pen on my past models. Anything better?

Some people use q-tips. I prefer to get the decal out of water with my hobby knife, then position it with a toothpick.

Yep, slightly moist Q-Tips and toothpicks are the main choices. I’m a Q-Tip user.

I third the Q-tips. They are by far the easiest and most accessible things to use.