Your stance seems fine and i bet you will learn some great tricks in no time.
there are many buttering videos online, combined with what you've seen from SA you should have more than enough learning material for simple buttering moves.
i just want to share some slightly more advanced moves to give you food for thought :P
1. i find it easier/cooler to tailpress by starting with a nollie then shifting weight to the tail. you can press longer and it looks nicer. similarly, jumping a 180 or 270 into presses helped me learn my butters because i can use the rotation in the jump to help me spin while i press, and again looks nicer :P please note that you need to make fine adjustments with your toe/heel to complete the full 360 rotation.
-ps. to get into a deeper flex when you press, bend one leg and extend the other, then slowly straighten/extend the bent leg and your press will be much higher. be prepared to fall a lot before you figure out the balance point though.
2. you can link your pivot 180 noserolls with a sudden shift in weight to the switch nose and then spin another 180 or 360 air, looks very cool. similarly, an easier version would be pivote 270 noseroll + switch 270 out
3. you can also try jumping 180s and landing with tailpresses and continue to this nonstop. similarly, you can always link ground 180s or 360s with butters.