, trimming isn't my favourite thing in the world either!
I have a pre-existing back injury, and I can't for the life of me find my misplaced back brace I should be wearing when trimming. I do have access to a good farrier, but he's retired now. He's still happy to trim in the middle of summer when my horses' hooves are like marble, or if I have an injury (like the broken foot recently), but he says, "You're doing a good job, you trim so I can go fishing!"
I know what the other farriers in the area are like - the horses' feet in this region generally look shocking - and would rather trim myself.
It would be lovely if one of us had a helicopter and could fly over and mentor you in person. That's always so helpful, and so stress-reducing for the person trying to learn. Are there any barefoot trimmers in your area who might do that for you?
If you use the rasp to start with, you can't do accidental damage - just like when filing your fingernails. However, rasping is hard work, and nipping off the obvious overgrowth first will save you a lot of sweat and sore arms. (You're going to have such toned arms from doing your own rasping though, you may as well cancel your gym membership!
) If you post photos of the underside of your horse's hooves with the shoes off, we might be able to see some guideposts for you. Some horses are very "trim along the dotted line" and easy - some are a bit less obvious.
Did someone discuss farriery tools that make things easy versus a pain in the neck? @gottatrot
was talking about that on a recent thread, maybe she could link to it? She gave an excellent description of the sort of nippers that will make your life easy. Also I must mention that I had a really bad type of standard rasp from the horse equipment store when I started, and when the farrier let me try his, I was amazed how easy it was in comparison. He also showed me how to sharpen my own rasp, which he will do after every 5 horses or so, and it makes all the difference in the world. And I recommend leather gloves, long sleeves and nice sturdy jeans for trimming. I've got a scar on my left arm from slipping with a hoof knife when I started! It was summer and I was in a T-shirt because I hate getting overheated...
I think the whole question of boots can't be revisited until your horse has reasonable feet, and that's going to take time. Successful use of hoof boots depends so much on having healthy hoof angles and relatively short hooves - like mustangs in the wild. Do you have any soft footing you can ride on while your horse is getting rehabilitated?
Good luck, best wishes, don't give up, you're a trooper to take this on and it will be a bit intimidating at first, and perhaps even incredibly frustrating at the start, but we've all been there. I'm hereby going to give you a little booklet of ten free ranting vouchers, redeemable anytime, for when you run into confusion, difficulty or whatever. If that happens, rant away! I will lend you my (virtual) ears. And there's a heap
of people on your thread who will continue to support and encourage you.