You need good pressure and a clean, well-oiled set of clippers to avoid clipper rash. Also try to minimise how many times you clip over the same patch of skin, and allow the blades to cool if they get warm (hopefully you have a spare you could swap in if this is an issue and you're under time pressure?). I like the suggestion above of an animal grooming course, but would also like to suggest asking one of the other nurses to guide your next one or for them to walk you through their next one, just to make sure you have all the details right so you're minimising that rash risk!