Our Lowe's friend, Justin, was working when we went in to buy the paint, and he suggested Frog Tape. I would say a combination of the Frog Tape, rubbing the tape edge RIGHT before painting, and doing the first coat on the edge with a super dry brush was what helped us get such straight corners and little to no seeping.
I used a tiny paintbrush, looked like a little bigger than one of those Crayola paintbrushes from when we were kids. First I rubbed the section that I was going to paint with a rag, to really seal the edge of the tape into the texture of the wall. (I did 3-ft chunks of the edges at a time). Then I just baaaarely dipped the brush into the paint, painted underneath the edge, NOT touching the edge where the tape met the wall yet...when I was sure the brush was super dry, I used that tiny bit of paint to fill in along the taped edge. This made the coat of paint very thin . Next, I used a 2-in brush to paint a border along that line. Then, I would either move on to a bigger brush for the section underneath that, or go back and paint a 2nd thin (THIN) coat over the 1st section - the part where the tape met the wall. Then that section was pretty much done, and I moved on to the next 3-ft chunk of space.
