I'd recommmend downloading some texture brushes that closer resemble real brush strokes or load up the natural brush set that's included with photoshop (Great set here: click). Having your brush opacity or flow set to pen pressure helps a lot with blending (this can be found in brush settings, sometimes it's best to have one on rather than both). It's worth mentioning that the spacing can also affect the way a stroke can blend, a wider spacing helps for a more softer look but spacing it out too much will make it look like a pattern. Photoshop isn't very good at mixing so you have to kind of manually pick hues to do that, do you know about the shortcut for the colour picker? hold the ALT button to get the picker up and then release it to go back to the brush, I use that constantly. I've seen people do great things with the smudge tool so that might be something you want to look into but I wouldn't use it with a default round brush tool. Hopefully some of that helps!