I find there are 2 different kinds that are subtly different - those where one diabolo is grinding on the stick with a wrap and those where there is no stick grind. For the stick grind version, just grind on the stick with a fontwrap and go for it. Both your right and left hand are going to be active. Doubles and triples are quite possible from this position, but the grinding diabolo does slow down quickly.
For the wrap only version (which I find myself typically doing), I find it much easier to already have the diabolos going in an anti-clockwise direction. So, start by doing a long vortex and then as the diabolo comes around put another front wrap on it, sort of lift it up so it goes weightless, and keep swinging with your left hand. The momentum should carry it through. This one is nice because you don't have to grind a diabolo. Grinding with a wrap usually pulls the diabolo a bit out of alignment. That’s not a problem with the grind-less version. The grind-less version also fits nicely into 2 diabolo combos.