If you can slip the clutch enough to pull away from a stop light without a Nascar style start, then you can slip it on the launch at the track. Side stepping the clutch is just mindless and gives you no control at all.
You just need practice on hitting the engagement point on the clutch just right. Bring the rpms up to a steady 3500 and slowly let the clutch out. When you feel the car just barely start to creep forward, push the clutch in just a hair so you don't creep forward. Then, give it much more gas and draw the clutch out an inch or 2 without letting it fully out. This will help you find the engagement point where the clutch needs to be on launch. I do that method everytime at the track, but be aware that sitting at the line with the clutch partially out will start heating the clutch up, so don't do that for too long (my clutch has gone 70k miles and at least 30 passes at the track this way).
As for launching on the nitrous... try launching this way without the bottle first. You will generally be at part throttle while slipping the clutch and then got WOT after the clutch is engaged. This method would then transfer well when you hook up the bottle again. Launch without the nitrous, then when the clutch is engaged, put the petal to the floor to start spraying.