To get one going from start to ready to show is going to take closer to a year.
Western Pleasure is far more than just riding a horse decked out in western saddle, and that takes time with a trainer.
But 4 weeks? That doesn't even begin to start.
If you plan to show, you need to find a trainer that does Paints, as I am guessing this horse is that? And is it registered?
Horses make me a better person.