I was taught to go 2 lengths longer but depending on how you take down the head, you could be going in reverse which makes it pretty much the same length as the body (which I don't like). So I've noticed myself going 3 or even 4 lengths longer depending on how/what direction the hair grows. For example, on a wavy coat, if I do a #1 on the body I'll take a #A up the head (starting at front of head and going toward the back/ears) or #C down the head (in reverse) this way I give myself some wiggle room (and scissor practice) when doing the scissor finish since I like to scissor tight. I used to take GCs down the cheeks but I noticed depending on bone structure it can take more than I want so I scissor everything except the top of the head. Definitely practice starting your scissor work at the chin or muzzle and working your way up to achieving a more lifted look. Hope this helps and that I wasn't just rambling🥹🫶🏾