So, I actually do a lot of towel projects. Either a hooded towel, towel sets as gifts, or for myself of course! hehe
For embroidering on towels, I hoop a piece of tear away stabilizer. Spray adhesive on my tear away and pin the towel to it.
Don't try to hoop your towel! It's just a big pain... way to thick!
Once you get it pinned, spray lightly a piece of water soluble stabilizer (WWS) and lay it on top. This will keep all the little pokeys from coming through while embroidering.
When I first started learning how to do embroidery, I thought that surely the WWS wouldn't make that big of a difference. Boy oh boy... I was wrong. Don't embroider towels without it! They look so much nicer!