For skins you need larger pots, cook them for about 40mins in the oven (As if you were doing jacket spuds) then take them out, cut, and scoop most (not all, you want about 2cm of spud left)of the potato (make into mash and freeze for later date maybe) then make up some oil and any seasoning you want, brush it over with a pastry bursh.
Cook for about half hour, skin side down first turning over after about 15 mins.