I also use Lister Star clippers. The horses must be squeaky clean (groomed thoroughly, bathed, and completely dry; I used my horse vacuum to blow them with the crevice tool this time, before bathing, and it worked great).
Usually, I’m on my own. My horses (quite a few over the years) have always been very cooperative - I think they know how good they’re going to feel once the heavy fur is gone (they’ve all been hairy types). I either put manes up in running braids to get them out of the way, or I use alligator-type hair clips from the beauty supply store.
I do high trace clips (complete neck, shoulders, chest, halfway up the belly on the sides and the flanks, forearms and gaskins but not past knees or hocks, underneath the jaw but not the rest of the head). I’ve tried chalk and tape to outline the trace clip, but haven’t had real luck with it on their squeaky-clean plush-textured coats, so I no longer bother – just eyeball the clip in relation to myself with the occasional check from one side to the other.
I do the neck, shoulder, chest, forearm on one side, then the other side; back to the first side for the belly, flank, gaskins, then clip the other. The idea is, if I must stop for any reason (although it’s never happened yet) and come back to the clip later, the horse will be somewhat balanced in comfort and appearance.
For blending clipped into unclipped areas, I change the direction of the clipper path (against hair growth for clipping large areas, then with hair growth to blend in with areas that will remain unclipped on lower legs). If my husband happens to be handy, I have him hold each front leg up and pulled a bit forward to make it easier to access the armpit area. He also helps by holding the tail away from the hindquarters being clipped, and by moving the horse’s head slightly towards him away from me as I clip the throatlatch area and under the jaw. But, with all of my horses, I’ve always been able to do it all by myself if necessary.
For making a clean, sharp edge between a clipped/unclipped area, like on the “waterline” halfway up the sides along the belly and flanks, I hold the clippers upsidedown and perpendicular to the side of the horse (hope that’s clear) and make a very short, downward stroke (think trimming sideburns on a man).
I find that pausing quite frequently - every few minutes as recommended by Lister - to clean the blades, and lubricate the clippers, works very well. This comes to several brief breaks per horse, keeping the blades cool and the horses cool about being clipped.
A pocketful of little treats is always handy; I take care to give the treat while the clippers are running, so the reward is for tolerating them, not for when nothing is happening.
