Does Kirbydabess actually play Kirby and you Kirby ditto'd or is it just a name? I can't give advice for the Kirby ditto, I've literally lost every Kirby ditto I've done offline and on Wi-Fi since Apex. XD
As for Kirby vs Snake... I believe that MU's 55-45 Snake, Snake wins, but only slightly (I talked with Chu last tourney I saw him at and he said it might be Kirby's favor if he can get Snake's power, but I have no idea how to use the nades ^^; ). For how I play the MU, I like to zone Snake a lot out of his tilt range, but just barely. I like to scout and see what the Snake will do if I get close.
If the Snake drops their shield and tries to punish with tilts, I learn their timing so I can space a bair to hit them with and if the Snake shields a lot and tries to use grenades more, I learn their timing then grab them. It's kind of hard to explain how I learn timings, but I learn as I play my opponent. When you DO hit/grab a Snake though, do your best to make your hits count. Since Snake is limited in the air, if you can get him in the air, you can really get a lot of percent. Spacing is extremely crucial in this match-up, you don't wanna take 20% from mis-spacing and getting f-tilted. Speaking of f-tilt, if you powershield the first hit, grab it. If it's not a powershield, just hold your shield or roll back (if you think they're not gonna do the second hit and grab instead), it'll push you too far back to grab and you'll eat free percent from the second hit.
I'm not exactly the best at killing in the MU, but if Snake in f-smash kill percent and you've learned when they're most likely going to drop their shield, if you're behind them, you can f-smash them if you know when they're going to drop their shield. Snake doesn't have an invincible Up-B, so he's not like MK or Marth where he can just reverse Up-B you out of shield. Another way I like to kill is if I got Snake in the air and he tries to recover to the ledge, I f-tilt if they aren't in f-smash kill percent. The reason for this is because the knockback on f-tilt isn't too strong to the point where they can DI up and recover high again (I think... I might be wrong if they're at really high percents) meaning they have to recover in a predictable range.
Also, when you Gonzo combo a Snake (f-throw -> uair), if they know the MU, they'll probably pull a nade after the f-throw to stop the uair from further combo'ing as well as deal percent on you. If they do this once, then you know they're gonna do it again if you grab them at low percent on their next stock, so what you can do is hammer instead of uair to get more percent since you're not gonna be able to string anything after you get blown up anyway. IF you do choose to hammer though, this can actually be jumped out of, so if the Snake starts jumping out instead of pulling a nade when you do the Gonzo combo, go back to uairing, the guaranteed percent is worth it more than a few more percent (not sure how much more hammer does than uair ^^; ).
I may not have given the best/most detailed advice, but I just woke up and figured I'd give some basic info I know on the MU. XD