Well, that wasn't so bad. I've now manually searched for and refollowed (or follow-requested) for the new account the ~70 folks I was following from the old account.

I've pinned in the new account 4 of the 5 hashtags I had pinned in the old account (archaeology, dnd5e, criticalrole, criticalroleart) and decided not to pin mastoart as it's just too busy a hashtag, though it has its rewards.

And I've copied over my preferences (and added 'opting out of search engines').