I usually sheet in to fill it, then immediately ease off again to bring it back to it's correct flying shape. If that doesn't work I bear off a bit. All this hapens in a matter of a second or so - you could almost say it's 'both at the same time'. I guess it's just a sort of intuitive reaction, I don't really think about it, I just do whatever is needed in a particular situation to keep it flying.

If I'm trying to keep high (perhaps to lay a mark) then sheeting is my first and primary option. If it's a standard downwind then I'll do whatever is going to work best.