In the past, I've only ever got the pocket with the heel on but found it a bit fiddly and a little scary - very tenuous position with feet high and a prospective cocyx bash (and I invariably chickened out of going for the gaston anyway).
You might be right re conditions though, I was trying it again on Sunday and greased off the sloper everytime; and on Fertile Delta couldn't commit to the move to the sika'd hold from the slopes (and I had been hoping to put away the sitter). Shame really - it felt like conditions should be tres bon (cool, slight breeze) but the holds all felt rather toothpasty, no matter how assiduously I tried to remove the accummulated chalk. Still, finding an alternative means of doing Mr Skin has thoroughly reawakened my love of ledge-shuffly linkage.