We (my moh and I- we did one for her too) did do one letter at a time, and used a ruler to make sure it was even and they were!
I know we could have bought the words already written out, but we couldnt find it in the store and we really wanted to make the shirts... It wasnt all that hard...we made two shirts in about 45 minutes, but we did a lot of bullshmoozing while we were doing it
Wasnt hard and a lot more cost effective than buying the shirts, fh actually saw it and asked where i bought it, he knows how not craftsy i am, and said it looked professional!