how can I socialise/adjust my existing cat to a new kitten?

my existing cat, ollie, came to us as a feral, and has always been exceptionally hostile to other cats. we had three at the time, living with my mother, and eventually he adjusted to them and even seemed to make friends, grooming them (even the girl, Ginny, who herself is very hostile to other cats).

we've since moved into our own house and took him with us, and have now gotten a new kitten. however, ollie is back to showing his aggressive ways, not just growling and hissing but also making attack motions in am attempt to intimidate the new kitten.

he'd adapted before, which was why we were hopeful of him adjusting, but I worry that now that he's the senior resident he might feel like this is an intrusion on his territory and might never learn to be tolerant of his new housemate.

does anyone have any experience getting aggressive cats accustomed to new kittens, or any advice on what we might be able to do to help the process along?