I found with the Gypsy on the Chippy that I could prop it without curling my fingertips around the trailing edge of the blade. I just bent them a bit at the TE to give grip, but not bent so much as to be curled around the blade. The object being that if it kicks back it will not take you fingers with it.
The swinging action is a progressive but firm downward swing while stepping back and to the side. On a long stroke low compression engine like the Gypsy you only have to pull it over TDC and it will 'flop' round the rest of the half-revolution, bouncing to a stop between compressions if it doesn't fire.
Also, on the Gypsy, listen for the distinctive 'click' of the impulse mechanism on the RH mag. No click, it'll never start! I once arrived at Barton to find a ring of onlookers around our Chippy while a relatively new member of the group tried to swing it into life (one of the many periods in the aircraft's life when the battery / starter were u/s). He'd been at it for 3/4 hour solid and was knackered. I could hear as I approached, the absence of the 'click' (it's quite loud).
I invited him to have a breather while I whipped open the RH cowl, whacked the mag with a large spanner, and fastened the cowl again. It started first swing after that!