>>53567151chain breeding is an enormous waste of your time, don't do it.
you don't need a shiny ditto, just a ditto with shiny genes. every pokémon you breed with that ditto will be 1/64 shiny odds.
you can use repel trick to find them in Red/Blue's cerulean cave at better than 1/128 odds. on one floor there are ditto at level 67 and they're the highest level pokémon there. if the ditto's defense is 82, and its special is 72 OR 82, you have a ditto suitable for breeding.
and i can verify that such a stat spread can generate in gen I since i have one.
if you can't trade from a gen 1 game, then you can instead catch dittos in the grass on route 34 and deposit them in the daycare alongside the red gyarados. if your ditto says it's "brimming with energy", it has shiny genes. this will still be faster than chain breeding.
tl;dr chain breeding is a cringe meme and a bad idea, it takes longer than just finding the ditto and using that, plus you need ditto if you want to breed a shiny genderless mon. thanks for listening