The V2's have a black plastic cap that threads onto the bottom of the shock body itself. If you change your shock oil fairly regularly, the shock oil you drain out should be pretty clean looking. If this it the case, you can just get as much of the oil out with a clean towel or q-tip and then refill with the different weight. Any left overs won't make enough of a difference for you to be able to feel. If you let your shock oil get dirty and gnarly looking (shame on you! just like my kids!), you might want to consider taking the shock apart and replacing the o-rings at that point.