I'm using enough product but hair still feels greasy. Could it be rinsing?

Yes. Immediate post-wash greasiness that doesn't improve after increasing product quantity almost always points to incomplete rinsing. New Wash is a cream and behaves differently from anything you've used before - blasting water at the head without actively working fingers through it spreads the product rather than removing it. Rinse for at least two minutes while still scrubbing and moving the hair. The nape of the neck is where product most often stays behind. Adding water to the product during application also helps - it lightens the texture and means less stays behind at rinsing.