If you're asking how you actually get to fly the warbirds yourself (ie Take part in the Duxford days etc)it's very much a closed shop of being 'in the know' I think.
After all,these machines are worth millions so they don't let you fly just 'cos you can fly - you've got to be good.
Ex-mil fast jets would be a good start or write to Stephen Grey who owns TFC (The Fighter Collection) at Duxford. The Old Flying Machine Co is also there. Buy all the mags and read about these people.
Interesting point is that when you go to one of these old timer airshows, the age of the pilots is quite advanced so OUR DAY WILL COME.
Here's hoping. I'd love to do it too.
If you do get the chance - don't stuff up as someone did recently. Had a 'near incident' in a Hellcat and is out of the 'scene' for ever. Quite rightly I suppose.....