For "nil wind days" / thermic and variable direction, I use a power assisted inflation. Taught to me by Michel Carnet.
One large step back from lines taught. Half to full power for 10 seconds whilst leaning forward (just enough to direct airflow above leading edge) this creates airflow in towards the pilot's face as air is drawn through the prop. (This can be seen by watching the grass at your feet.) Power off and then begin inflation. I only reapply power once my wing is at the 13:00 position and I've checked wing symmetry.
I haven't failed a launch in quite a while and often manage with this technique when others struggle.