I have 14, and I clip all their nails from time to time without any help. It takes about an hour to do them all in the same session. You can also spread it out more, for example doing one bird per day until they're all done. Write down the names as you do it so you can keep track of who's been done and who hasn't.

There are perches that will file down nails, such as sand perches. Alex's nails seem to stay a good size, but Lucy's are due for a clipping soon (and they use the same perches). Makes me wonder if it's an age thing.

If you do decide to clip them for he first time, be sure to have some septic powder near you to stop the bleeding in case you cut too deep.

Some people don't recommend those perches because it is rough on the feet.

Well most tree branches in the wild aren't exactly "smooth" either, so they could probably get used to it. it really depends on the quality of the perch. The crappy ones are bad for the feet, but there are some really good ones for that purpose too.

I have those perches but my birds prefer to spend their time somewhere else
I looked today at the way they stand on flat surface, and they seem to be able to place their feet flat, some nails are not touching (always true rear nails), and a very few nails just barely touch the surface - usually front nails (but foot is still flat).
I guess we can still wait a little/

It's mainly the sandy covers for dowel perches that are frowned on. Dowel perches aren't great for their feet to start out with and putting a rough cover on it makes it work. The concrete or sandy perches with irregular contoured shapes are considered to be OK, as long as there are other types of perch in the cage for the bird to use too.

I get the impression that individual genetics have an effect on how fast the nails grow. Some of my birds have faster-growing nails than others. Lucy's daddy Buster has fast-growing nails so it's possible that she inherited it from him. Shodu has slower-growing nails.