I think scratching is almost like foot stance in skateboarding or surfing.. Regardless of your strong hand you'll sort of just jump straight into it (Think metaphor of cunts teaching surfing and they lay down on their stomach and then jump up with a foot forward really fast, and that instantly works out whether you're goofy footed or natural) I think walking up to the decks and prep'ing to scratch you will naturally set yourself up how you need to be I'm right handed yet my left is fucking lightening quick on the fader and I have my right placed on the vinyl I can't remember the last time I tried the other way, but sometimes I do hit the fader using my right to get an epic granulizer effect, but wouldn't be able to do it if I was setup on the complete other side