Acrylic Paint (DO NOT USE WATER COLORS)
So the acrylic paint won't leak to the back of your shirt, and to make it easier when putting on the tape letters, place some cardboard on the inside of the shirt. Make sure it fits perfectly.
When placing the tape on the shirt, you want to make sure it's completely center. That's where a ruler will come in handy. Marking it with a pencil is a good way to keep everything straight. It will wash off in the washing machine later on.
Now, you can't really see it, but I put the words 'Prima Donna' on it. If you have words that are curved like the 'D', you can make a square with the tape, pick it up, and use your scissor to curve it.
For the painting, you're going to want to bring the paint 1/4 of an inch out from the tape, and inside of the tape if you have any letters that have an opening in them. You could bring them further out, but they might end up looking a bit messy.
After letting the paint dry, take the tape off. This is how it will look (Above picture). Clean and crisp lines. In order for the paint to not be stiff when you wear it, throw it in the washing machine. It will wear the paint out a little bit, and make it more flexible. If you're using acrylic paints, you won't have to worry about the paint washing off.
Thank you for reading!