A couple things to note after playing brawl with snake mains for a while:
Dtilt twice... It works, I swear.
Pkt nades only if you are really good at aiming the pkt. For standard approach on the nade barrage, I say use either FHpkFire, PKjump, or just FH towards him. You want to keep some height off the ground, because you don't want to explode or have your opponent throw nades at you when you're pkt'ing and get hurt. Overall, get near him, which seems odd enough when talking about snake.
I REALLY LIKE THE GROUND AGAINST SNAKE... there is so much more you can do. I've said before, dtilt. It is insane. Get behind him, use it twice, and you've got at least a jab combo on him... If not, you messed up in execution. NOTE: you must followup with something immediately, or else you put yourself into a bad position. Ftilt can be used to punish the laggy stuff he uses at close range. Dash attack has range, can potentially set off nades, and is fairly quick, so you can also use it for punishing. Utilt is for airdodging down or immediately after landing a uair. Jab combo sucks... The smashes have range, so you can use those if you place them well. You want to get snake grabbed, and if you don't get to the ground eventually, you can't grab him.
Pkt is insane for stopping his cypher recovery when he is too high to dair or whatever. If he goes up enough, we get a free kill. If he stays lower, we get at least 8%. if you don't believe me, try a different approach to how you use your pkt against snake. Every match, I've gotten at least 30% onto my opponent because of him using cypher. You just need to time it and make it follow him in a way so that if he does airdodge, all you need to do is loop around to follow him. You can also hit him out of the cypher with pkt, so do that if you need to.
If you get your shield utilted, don't drop it... If anything, roll someplace. Don't EVER just drop the shield. Your options are: roll, jump OoS backwards fully, SH fair/nair OoS full forward. The latter 2 depend on position. I say the first of the latter only if you are very near the outer edge of the hitbox. The last is if you were initially very close to the snake.
Possibly more coming. These are my gimmicks/strategies that help me to overcome snake. There are lots, but I'm tired.