Ashtanga frowns on props but they can be useful. I don't necessarily suggest you should use them during your main practice although I did use Nike grips every morning for a few weeks over July/Aug. If you have some spare time in the evening try some jump backs and jump through's using yoga blocks to give you the extra height. Takes away some of the fear of rubbing your feet along the mat or smashing your little toe. Best of all though, you start to get the idea of what a full floaty Jump Back feels like. Again your getting used to how you should be shifting your body weight and exercising your core. You can hold your lolasana in the middle and just generally play around with it. I preferred Nike grips to blocks but either are fine. Also socks are useful (grip socks, great if you can find some) as you can slide along the floor (try it in the kitchen or bathroom if you don't have a wood floor) you don't get hung up on your sticky mat. I think it was John Scott who suggests putting a t-shirt on the floor and sliding it back and forth through your Jump Back. I'm also a big fan of microfiber towels as they are really soft and you can brush over the top of it without rubbing your toes raw, manduka make one. Manduka's black mats are also good when they get good and sweaty as your feet will slide through.