So, how exactly do you build trust?

[circusseal]

(minus going through the shoals and interacting with the statue at Azure Coast, of course)

I know feeding treats and winning competitions, and apparently petting your horse as well, and the Soft Brush. Are there any other methods? What about training them in the arena or going on trail rides? Surely riding them counts as "spending time with them"?

[TheMiles]

I've honestly never done anything but ride em around and gained trust.
In my newest playthrough, I'm on day 21 or so of spring and my first horse is at 87% trust without me doing anything but riding it normally.

I'd say the new area and method are there to just gain trust quicker!

[AlbinoTiger]

Riding, lunging and leading your Horse/Foal can also increase trust