All you have to do is target the horse you want to level to 4 bonding level and choose to lead it.

Below I show the most ideal leading location, this is one of the longest safest most secluded straight tracks in the game and no trains spawn there.



The idea is to go from one side to the other leading the horse in a straight line.

Horse bonding levels only during Free Roam. It won't level during Legendary Bounties, and other missions that create their own lobbies. If you level your bonding there after the mission end it will be returned to the level it was prior to when mission started.

You can also buy the Javelina Tusk Trinket trinket from Gus if you have Naturalist role unlocked. It forever speeds up bonding by 10% and costs $500 and requries the following ingredients: 1 x Javelina Tusk, 1 x Elliston Carved Bracelet

I suggest putting something heavy on the W key, like a heavy die or some other heavy but small object that can hold the key down. Then you will only have to aim a straight line with your mouse. Once your character reaches the end just use the mouse to turn around and sit back and relax.

I got my 10 horses all to bonding 4, each in half an hour. I spent that time reading, only keeping a little watch now and then, turning the horse around or adjusting the path. Maybe now that lobbies are nearly empty, a predator will spawn to attack you. Prior to empty lobbies I barely saw anyone in that location. Hell, sometimes you can even go make tea or take a quick bathroom break and it will still be going in a straight line other times it can be stuck on a rock.

So this is a very efficient way to level a horse instead of feeding, brushing and riding it for hours, especially if you have many horses that need leveling. Saves you money from feeding too.

RDO in itself is a great game. If you like winning (possibly in PvP) or grinding i.e restocking the trader, moonshiner to sell different moonshine, you enjoy collecting, doing various daily challenges, have fun with horses, or you enjoy showing off your abilities as bounty hunter, or even like tracking animals as naturalist. Over time you may accumulate a lot of wealth and despite occasional cheaters and connection issues, it is a really really amazing experience.

Please, have fun and enjoy and be well!