We groom in stages---1 day I do the face, another i trim the feet and privates with a clipper and the 3rd day I trim the body.
Advice:
Start by taking a little off, you can always take more! But, you can't glue it on once it's off.
Trim in vertical pieces--instead of horizontal, it gives a better flow!
We usuallly do it with 2 people--one to care for the dog-1 to trim!