Dealing with his Shuffle game:
Get better at wavedashing. Kirby's wavedash is fairly small, but if you dash in a perfect wavedash it will carry you a little farther. Learn to chain these together and do your best to outspace his aerial approaches. Fox has a lot on Kirby.
Edgeguarding:
A good fox will almost always try to recover high in the air (when the situation permits), because Kirby's options don't even extend into that range. The moment you see his firefox evading you, you MUST react or you won't be able to catch him. Don't throw any attacks, just get on the move.
Keeping his damage higher than yours:
Up-angled Ftilt is a good one to use out of wavedashes. Uptilt will be able to juggle Fox until he DI's left or right. When he begins to DI, I like to upsmash and then upair. Use bairs to get him off the stage.
When you're recovering:
His shinespike owns you, period. Try to anticipate him coming with an upair, it's pretty much the only defense you have. Upair outranges the shine, iirc. The hit will either be good enough to ensure your survival or it could possibly even stagespike him. Sometimes I like to jump away from the stage when I see Fox coming and bair. It can be harder to connect and you must know how to set Fox up for it (which, I'm afraid to say, is your own complicated metagame business).
Overall:
He's fast and upsmash will kill you at extremely angering percents. Make sure to taunt if it's ever appropriate, perhaps more than once at a time. If you feel a Kirbycide, make it count. Fox isn't Kirby's most difficult opponent, as his range allows for a little breathing room; it is an uphill matchup so keep your head in that game and cheap kill that sucka!
