The muzzle area is probably the hardest area to shave so take your time and use a DE if you don't feel comfortable.
Even with my big conk I can still use a 8/8 easy enough for my top lip. (I do grow a tasche now and again) I use a scooping sweep for want of a better word for the 1st pass at 45 degrees to my nose and straight down xtg for the 2nd pass.
For my chin I go straight down then at 45 degrees which is atg. I make sure I really stretch my skin too.