I tend to just dash dance around and rack up a little damage from pillspam until I can set up for chaingrabs. If done correctly, f-throw/b-throw off of a ledge, and depending on their DI, use bair, dair, or gimp with up-Special or Cape.
Something I make use of if they recover high or right above the ledge is the broken hitbox on u-tilts. Seriously, it out-priorities a majority of what a spacey can recover with if you time it properly, and it comes out quickly and sends them either upwards to be followed up with an aerial or farther to the side, which sets you up for a cape. u-tilt is your safest option for falco, and cape works for both spaceys obviously.
Doc actually has some pretty good options for gimping fox, falco, CF, Ganon, marth, puff (only if they're nub enough to rollout), among many others. That paired with the fact that he has the most chaingrabs in the game is what makes him good
It's all situational for what you should use, and you shouldn't use one option too much in the event that the other player expects it to happen. Mix it up occasionally.