I think the best advice is to lose weight gradually, tone up as you go, and keep moisturising.
A body brush is used to increase circulation, stimulate new cell growth, and to exfoliate dead skin cells on your body. You can buy them from Superdrug/Boots and places like that, they sometimes come with a long handle to reach your back, otherwise they're round/oval and just a bit bigger than the palm or your hand.
I think they usually come with instructions but I think you're supposed to start at your feet, and work upwards using short strokes in the direction of your heart.
I've also heard that it's useful to keep drinking lots of water (which is a good thing with Xenical anyway). Hydrated skin is more elastic than dry skin - so the water can only be a good thing!
I think a lot of it depends on genetic factors though, and whether you've lost/gained significant amounts of weight in the past.
When I lost 8 stone a while back, my skin was a bit of a flabby mess in some areas to be honest(stomach, bingo wings, thighs) but there's no way I would want to stay big, just to avoid the loose skin. The best any of us can do is to follow the advice and hope for the best!