HALP!
 

I'm trying to remember this game.

It was on the SNES I think. You started out as a poor farmboy or whatever, in the first area was this goat, and if you didn't give him food you hate to reset or he wouldn't leave you alone

You had this magic paintbrush that you touched to a painting and it took you to this castle in the sky or something.

I also remember a dungeon in the water.

Sounds like Soul Blazer to me.