Are you putting liniment on before the workout? Are you putting it on top of fly spray?
After a hard work, I will cold hose each leg for approx 10 minutes each. I'll dry the legs well and then rub the liniment on. Check to make sure you don't have a concentrate that needs to be diluted.
Some horses are very sensitive to liniment and you make have to water it down a little bit.
As for wrapping after workouts.. I used to ride for a coach who had us wrap after every decent workout. What I saw happening is that the horses leg structures lost their "tone" and they would start to have problems stocking up. It got so bad that if you failed to wrap a horse after working, they would stock up so badly they were uncomfortable. I stopped wrapping after every workout and only did it after a particularly heavy show or work...no more than a couple of times a month. I stopped having any trouble with stocking up.
This is just my experience and observation. Some times we hurt out horses in the desire to help them.
I would also check and see if other horses in your barn are getting rain scald/rot. It is very common on the lower leg and, because of all the rain we have had, it is all over our barn. Once it is in the soil, you will have recurrences for-freaking-ever. It presents itself as little bumps that eventually scab and form "scab mats".
Does it look like this? Rain scald/rot.