I've had a lot of success with this stuff:
I found it at Joann. About $11 for 20" x 3 yards. It's transparent, so you can trace your design. I like to use a ballpoint pen, as marker (even permanent) tends to smear.
I have found its best not to have any straight corners; cut your shape in more of a circle or shape with rounded corners and then iron using medium heat and no steam. Iron for about 5 seconds and check to see if the stabilizer and fabric are fused. If not iron a few more seconds until fused.
I don't usually use a hoop to stitch knit, because I feel like I have better control without one. Totally Stable isn't fool proof. If you pull too much it will release from the fabric. I learned simply by trial and error. Be sure to use a sharp needle and take your time.
To remove Totally Stable, peel it off. But be really careful around your stitching or you'll pull out the stitches. I think it works best to hold an area of stitches with my left thumb and forefinger and then carefully tear away the stabilizer. I use tweezers to remove any small pieces that stick under the stitches.
