It seems like Donkey Kong mitigates a lot of Bowser's greatest strengths. No grab releases, he survives just as long as you and kills just as well as you and I think his F Tilt and D Tilt outrange everything we have except Firebreath (could someone confirm?). Neither character will be gimping the other so it mostly comes down to the two of you slogging at each other until you're in you're respective high kill percentages. DK's stupid grab range also means the living in shield idea has to be more cautious, a lot of things you would normally do (e.g. running shield to react as an approach) become unviable.
I agree with Gen, B Air isn't that big a deal, thanks to Bowsers wonderful OOS option in Fortress. You obviously should be abusing this the whole match, but that's no different to any other matchup. Klawhopping can give DK a lot of trouble, his limited mobility and Klaw's broken disjoint leave him with few immediate answers, especially considering he can't just shield and punish it. Firebreath is a GREAT asset in this match, DK's fat *** can't SDI through it like many others so he just has to take it and SDI out, resetting at neutral. If you can space Firebreath accordingly, it really affects the matchup.
couple misconceptions, i'll start from the top and work down, dk is slightly lighter off the side, but heavier off the top, his average weight makes him a bit heavier than you (and the heaviest character out there). On top of this he has the upb air brake, meaning he will not die from cross stage moves (you want him dead you have to corner him, hit him hard midstage, or hit him REALLY hard off the top). but his stocks will last longer than yours, on top of this he has preposterous amounts of knockback. punch is deadly in the 70-90 range, usmash in the 80/90s, fsmash around 90 (but who uses it uncharged?) dsmash around 110. i'm not 100% on these, i just knocked it up 20% from the normal numbers.
we can both gimp each other.... kinda. we can spike you, dair and either hit of fair (the sideways will still ko at most %s) is a gimp, you can edgeguard dk the way most people do, just keep hitting him back out until he either dies or makes it back. that said neither player can rely on gimps, but they are viable.
Bair is that good in this matchup, as it is our answer to bowsers oos game. bowser is one of the two characters that can go toe to toe with us on the ground, and while you aren't as good at it as diddy, that's still **** impressive (we can force snake to jump at us, SNAKE). your shield game makes our ground game risky, luckily we have well spaced bairs. your upb won't punish well spaced bairs, we're too far away and the attack ends too soon, if they space badly/try to double bair, go ahead, its a free punish, but a smart bair spam gives bowser lots of problems and lets dk poke at his shield.
klawhopping is not as effective, as upb and high angled ftilts both beat it.
6-4 dk, bowser should be grounded and forcing us aerial, dk should be spacing bairs. your ground game keeps you in it, but the bair is really safe when retreated, so you have a lot of problems with it