Determining Muscle Aches

Recently, one of the festival's horses got in a fight with this mare who likes to instigate things from across the fence. From what I know, he got a bit cut up and there may be some muscle tenderness if she has kicked him. I know the mare likes to buck and kick others when she acts stupid, so I'm wondering.

My question is, how do you determine if a horse has muscle soreness? What would the proper means of aiding it to heal be?
We have some linament oil which, acts like icy hot for our horses, but I was wondering if there were any other techniques that could be used? Are massages a valid use? Also, would walking him on a lead line help for his stiffness, if he has any?

If he got whipped on enough to get cut he is sore. Give him some Bute and rest. If he is acting sore in certain areas then liniment won't hurt. I would think a massage may not be so great just yet. Yes, light exercise will loosen him up and stretch things out a bit as long as it doesn't interfere with any cuts that need time to start to heal.

Thank you. Should I walk him in the arena, or would walking him on normal terrain that has some hills and such, be alright? I plan on taking him out this weekend when I can go see him and make sure everything's alright.

Edit:
One question, though: What is bute?

Phenylbutazone is an anti-inflammatory given to horses. You have to get it from the vet. Light walking anywhere would likely not hurt him if he is not limping or obviously in pain somewhere.