First off YOU DO NOT win this match up by running away from fox or staying on your shield, use your broken hitboxes like uptilt, backair and down air, and also lasers to wall him out, fox can't beat this stuff, all he can do is tricky dash dances/wavedashes to beat your timings, full hops or go to the platforms. Start lasering as soon as the match starts, if he powershields, learn to powershield back: SHL and then shield immediately afterwards, watch Zhu, he's really good at doing this. If he full hops, stay away and laser, watch if he drifts backwards or forwards as he lands, if he comes down with an aerial or lands empty. There's not a whole lot you can do to challenge fox's full hop, the only thing that comes to mind to try to beat that is upsmash, upair or jumping and timing a super risky shine to beat whatever move he throws up (which requires 20xx like timing) when coming down. In my opinion is better to deal with what fox does after the full hop.
Other useful things to learn in this match up:
Combos on flat stage and platforms (watch mango, west and ppmd). Learn to combo the crap out of fox cause every shine counts and can be a determinating factor on who wins or loses.
Shine oos, buffering roll, shine grab, double shine, shield drop. DIng fox's upthrow, SDIng fox's upair, SDing fox's thunder's combo, teching smartly on platforms after getting upthrowd, teching drillshine,