A5fly, you might want to try this idea. Using some thin ( like .005-.007 ) thick mylar as carryers bag a layer of glass cloth onto the wings. You will still have to deal with the LE's but the rest of the wing will have a glass smooth finish on it in one step.

Jim B

What I am talking about here is a slight variation of the method used to produce glass/cf over foam composite wings. You cut the Mylar the exact shape of the wing getting as close to the LE as you can. Where the mylar will still follow the curve of the LE. ( this also applies to the wing tips ) Then you cut the Glass Cloth the exact shape of the Mylars. This is fussy work , getting the mylars cut exactly right , but it will save you a lot of hours of sanding.
Normally you would wax and paint the Mylars with your choice of color prior to applying the epoxy to the glass cloth, and this might be a good idea here as would give you color to look at when looking for flaws.
As far as doing both sides of the wing plug at the same time, I would suggest that you do this. Having the Mylars taped together at the TE makes getting them in the proper position easy.
It's hard to introduce a warp or a twist in already built wing with the standard Bagging method.