It's probably one of the slowest rendering effects I own, but the quality is worth it.
Granted there are some techniques to reduce noise including After Effects built-in noise removal plugin (an adaptation of a well known software Adobe bought, Grain Surgery) but I prefer something a little more dedicated.
auto white balance, auto flicker remover, and shadow restorer just set the gamma clamp so that the top text layer(its off default) shows 25. then the flicker gets removed plus the shadows repaired. I've used it on some destroyed 8, 16mm stuff, and it works perfect.
it uses AE's shadow highlight effect automatically. you can use it manually on your own, too. More things you can do are AE's remove grain then the unsharp effect. finally, some technicolor put back in because technicolor footage often gets washed out.