|I've opted not to use interfacing on a blouse I'm making, but the fabric I'm using is quite thin and there's a lot of buttonholes. To prevent the thin fabric from getting pulled into the machine while sewing the buttonholes, I used a thin fusible hem webbing to stabilize the fabric.
The hem webbing I used was about 1 inch thick, so I cut 2 strips of it and basted them on either side of my fabric, over where the button hole was to go. Then I sewed the buttonhole as normal, and tore off the very thin hem web off of the buttonhole.
Buttonhole sewn over fusible hem web
I imagine that using left over pattern tissue would work just as well, as mentioned by Kim Winson here for stabilizing thin fabric during sewing.
If you want to see more pictures of the process (and want to read some of my babbling), come on over and check out my blog post on this tip. :)