Used this method a few times – very easy for just putting one grip on, but required a bit of brute force and fiddling for putting a half grip underneath.
If I recall I think I ended up putting the full grip on first then folding the bottom couple of inches back up. Then rolled the half grip and put it on top and rolled it down to the bottom of the handle – then rolled back the full grip and manoeuvred the half grip underneath.
Probably wasnt the easiest way of doing it – but I also had a couple of strips taped underneath to turn it from a round handle to a semi-oval which made it even more awkward.
Only did it for 1 & 1/2 grips once though –went out and bought a gripping cone afterwards.