How can I get a smooth buttery voice? What tips should I follow?

Good question, Gavin! I think you'll benfit from the tone tutorial: https://www.30daysinger.com/tutorial/getting-better-tone/1. 

Equally helpful would be listening to singers with the tone you want, and trying to mimic their sound. Nat King Cole comes to mind, as well as Ella Fitzgerald (in my range). Your ear and your capacity to mimic what you hear can teach you a lot about how to achieve a specific sound! I'll also add: make sure you're choosing songs in a comfortable range for you. It's significantly harder to achieve a smooth sound in an uncomfortable spot in your range (or at the extremes of your range).