When I use gel-based liniments in the past I’ll either mix it with a bucket of water for a nice rinse (purportedly it helps with blood flow, I don’t know if I could ever cite a scientific study proving it though) or apply directly on desired areas (typically soft tissue in lower legs - tendons) and rub in. No gobs/surface goop left, I spread it out and work it in. The gel liniments I’m most familiar with (absorbine’s is my big one, but there have been a few others in the past) tend to dry down fairly quickly so it’s not a huge “stick” risk/debris attractant, unless a horse goes down/scrubs the area in something before it’s dry.
Although I’ll definitely advise spot testing on your horse before putting on & leaving it/using it all over in any fashion. A few horses may react quite strongly to certain liniments (menthol and the essential oils are the big culprits iirc). I’ve used liniments under wraps before (typically post-show, overnight) but that’s only after I know a liniment isn’t going to incite a reaction.