I groom mines on a table (with a plastic tableclothe) outside the house in the garden to avoid the fur blowing on my furniture....and keep more clean the house. I have bought a cloak in a shop thal sells hair-dressers staff and It's fine to keep my clothes cleaner when I comb them.
I comb them almos every day since they are 3 months, but it seems that they never get used 100%, and if I don't comb them in a pair of days the nest session is more difficult.
My male sheltie has the pants as yours, terrible to comb them! Today I have decided (after cutting the hygienic circle under the tail...) that I'm going to cut with the slimmer scissors that part to make it easier to comb. I have used that scissors before and with good results, but in other parts and for the same reason. I hope he'll have the new fur soon, he is 6 months now.
If he climbs to my shoulder while combing, I hold him and give him kisses, wispering sweet things

....stop combing that zone and after few seconds continue....
I have 5 different combs and brush, but the best is the furminator, but after using others first...