Hey JLGrandAM !!
First of all welcome to the Board, you will love it here. I Promise
I throw stringsas well with sticks in clubs/raves. thats where i started. I use the round laces from Walmart 54". They have only given me Blisters once, and that was me spinning short strings un-godly fast. I hold the strings the same way you discribed.
First, make sure you are holding the strings tight between your thumb and index finger, if you dont they tend to rub more, plus youll end up with your strings changing length on you. i think thats your main prob. But now after those blisters go away, youll have caluses, youll never get a blistyer agian
I have used soccer tape, to put around my index fingers and this worked well.
I have made loops in one set of my strings, which makes it easier. You just have to cut them back, and tie them, making sure they are the same length. This works well. But with the strings that way you will hold them, and spin them like traditional POI. looped around two fingers, and using your wrists a little more.
Look in the POI lesson section, and find a close up picture of a hand movement, youll see what i mean. but it will take a few days to get use to spinning them that way, because it changes the path of the strings a little compared to pinching the strings between your thumb and index finger.
BUT, i did find some smooth Nylon thread, that works well. it doesnt cut into your fingers, and it spins fast as hell so be careful. Its hard to spin outside when the wind is blowing because it is lighter than the laces.
Hope this helps...
Email me if you have any Q's...
Super'