For the last while I’ve been randomising the dictionary of 3 or 4 character words and running down the list until I find something I like the sound of and is available. If it’s a well populated username base I might need to drop back to a list of all permutations of a-z in that length and do the same.
Coming from a country where no ID is required but everything still goes smoothly, I’m not sure strict ID controls actually are necessary.