If your horse is sensitive around neck area I would cut mane with scissors instead or use special blades to thin it.
- Bath horse a day or two before clipping. You will get rid of grease and dirt and it will massively help blades to go through coat.
- Watch teperature of clippers/blades. Check them every 10 mins to prevent skin burn.
- Oil clippers/blades every 10 mins or as frequently as required
- Hot towel your horse after clip. Use a dash of white vinegar in warm water. It will help to get rid of tiny itchy hair and calm sensitive skin.
Overalls are helpful to keep the flying hairs off your clothes! A face mask for preference.
I've found using medical gloves gives grip of you want to pull the main with your hands (as well as a comb) but if found some horses like this better! :)