I just did towels for my GKs. I experimented a bit... The wash away on top is the way to go. It is doable without it, but is smoother and looks nicer with it. I have seen mention of using " glad" press and seal, instead of the wash away... I believe I would try this. It will pull away once stitched.
I used tear away on some and cut away on others on the back... I couldn't tell much difference. I studied a number of tutorials before starting this project. All tutorials recommended tear away. They discouraged wash away on the back. stating the emb would not hold up well. (Thanks to CQ for showing us towels after many washings-- they look like they held up to me) I used white bobbin as recoommended....my towels were colored and it definately shows on the back side.. Next time I think I would try to use the same color as the towel. Would certainly make it look much nicer. The best thing I learned from my research was to use "sticky" stabilizer.. instead of trying to hoop the towel. I did hoop one practice towel, with difficulty( it was a lighter wt towel , than my project towels.) I loved the " Sticky" I will definately use it on otehr projects...