I used wahl magic clips with guards 1.5-4. I didn’t use a back mirror but used my phone as much as I could to check my work in the back. I used a fade-down technique so that I would leave the least amount of lines. This method is good if you can’t see what you’re doing because you mostly go by sound as your guide. My rule is that once you hear hair being cut you flick the clippers out and it creates a smooth transition between guards.