OMG! I see what you mean! Those really are quite the pants!
I have a furminator, but I use it rarely. Don't follow the directions that come with it and just rake it over the back. The idea is that you want to thin out the undercoat, not the top coat (guard hairs)
Whatever tool you use (furminator, rake, slicker, pin brush) make sure you use a line brush technique. You want to part the hair and brush from the roots outwards. When I'm grooming Indy's pants, I seem to switch brushes about every 30 seconds. Part hair, try rake. If tangled, switch to slicker to detangle, then rake, then pin brush. Move to next section.
Gee Rome has a video on line brushing with a furminator...I can't find the link at the moment. Her blog is Life is Better with Sheltie Hair.
When my hand is steady and I'm safe holding scissors, I will thin Indy's rump with thinning shears. I use a vertical line up the backside. Sometimes I will scissor the shears; other times I'll just use the rake side to strip.
The poop chute: I don't trust myself with a full blown razor, so I use a ladies bikini razor. It takes a little longer, but it does ensure that I can't get crazy and wipe out his entire butt in one fell swoop! I just go at it slowly, working my way down in a rectangle. If done properly, it creates a nice place for the tail to set.
