You could try cutting up photos with cloth folds to get the bits you want.
Then go into projection master (create new texture)
Set it to colour only
Set tool "plane 3D"
Alpha - one of the circles with a falloff
Stroke - rectangular stroke
Texture - load in one of the cut up photos showing folds
Put zintensity down to 0 and the colour intensity to around 60%
Then drag and drop the creases where you want on the model. When you are done, pick it back up from projection master. Go to tools>maskin>int (create mask from texture intensity).
You can turn the texture off now to make it easier to see. You can either go in with the tools and inflate etc., or go to tools>deformation>inflate (about 5) then smooth (about 10). Do that a few times.
This is mixing two techniques shown in videos in the 'artists in action' area on www.pixologic.com