if you are going for just smashaway, then yeah bair, fsmash, sometimes dsmash at certain points. but then again, sonic is god at killing off the top too. uair juggling. this is what sonic is god at. his uair has a unique hitbox, first he swings you in with a large sideways hitbox, then shoots you up with a large verticle hitbox. basically, this means his uair is easy to hit with. it is also fast, like sonic, so it is easy to juggle with. now for the fun part. so you hit your opponent up in the air, then jump, uair, double jump uair. NO WAIT, your opponent is so high in the air now, what ever will you do? up b. then uair. then taunt. this takes practice, so basically for sonic players only, this isnt a pick up and do thing, and it isnt a guaranteed ko, but it takes out heavies at as low as 80%, which is unheard of for sonic.
EDIT:sonics dtilt brings him forward a bit. his ftilt has 2 hits, and you can **** peoples recovery with using up b off stage to drop the spring on them. i have killed a very good marth player at 35ish percent using this.