I set my own rules that if the horse is scared of clippers, either sedate, teach the horse the clippers will not kill them, or I will not clip your horse. I have had to many incidents back when I first got into clipping other peoples horses and thought I was invincible, yea definitely not true. I got planted several times over the clippers and others horses.
With clippers, you get what you pay for. I think the best on the market is the double k groomers edge clippers. They run about 350.00 dollars and are best for professionals or someone who just clips a lot of their own horses. If you will only be clipping your own horse or two and not 50 million times a year, then a set of oster A5 turbo(one speeds are junk, make sure they are 2 speed) will last a lifetime. I started out with a set of those and taught myself to clip by experimenting with them on my own horses. The first few times were pretty rough looking, but hey, I learned to do it through trial and error, and lots of clipping clinics!!! It is truly an art to master. I still have my A5 turbo and they still see quite a bit of use to teach new babies to clip. I use them because they are louder than my double k and if they get broke by the horse, cheaper to fix. I like using the louder ones on the babies because this way whether I sell them or keep them, I know they will stand willingly to be clipped and not just scared because the other clippers are louder.
Just go out, get a decent set of clippers, and start seeing if anyone needs a trim, it is just hair, it grows back! So if it looks like crap, no big deal. I can offer tons of clipping advice seeing I clip my own 5 minis about 10 times each year and then on top of them everyone elses odd jobs or show clips for their horses. If you really want in depth details, you can send me a message and I could probably go on for months about what works and what doesn't work. Most of it is practice, but advice from someone who already knows what they are doing is A LOT of help.
You know how to make a miniature horse even smaller? Leave them in the dryer a little longer!
"Don't ever regret something that once made you smile"