Please help! Wedding horse shoe favours - any ideas?

I would imagine it would be easiest to clean them with a wire brush before you paint them. You could hang the ribbon the other way so that they are level & hang up straight like this:

Where are you getting the shoes from? If you are getting them from a farrier you could ask him to stick stud holes in the top of the shoes (which are a bit bigger than normal nail holes as you screw studs in to stop the horses slipping on wet, muddy ground) and would be easy to thread ribbon through & will probably hang straighter. If you use the nail holes because most horses have 4 nails on the outside of their foot & 3 on the inside it will be really difficult to get them to hang straight as you are finding!

To clean them up I would stick them in a bucket of water with a bit of cillit bang for ten minutes. Put your rubber gloves on & start scrubbing with a nail brush. It's a slow process but it's about the only way to get into the groove in the middle of the shoe to get all the mud & crud out.

See that is how i would like them to look! but sadly the reality of a horseshoe is that the nail holes are actually a lot lower down. My farrier has given me about 3 buckets of shoes that look like this:

so there lies the problem!!

Can you ask your farrier to put an extra hole at th top? or even wind the ribbon at the top & glue with a hot melt glue gun so that they are level.

Do you think glue will work? All the shoes are various sizes and I suspect that the holes may be blocked. I am not sure I can ask for stud holes to be put in - I have about 140 of them!