What is the correct procedure for forming brass from parent cases?

I have a parent case that I want to make a wildcat from. How much can you size brass each step before you collapse the case neck/shoulder? What step increment in thousandths is the minimum and maximum before this condition happens?
Thanks

[sniper2]

What case are you working with and where do you want to go?

[MachV]

The main factor will be the brass.Some will take a lot of abuse and others will have to be stept down a 1/2 caliber at a time(and that will be too much with some cases).
Got bored one night and tryed to neck every caliber I had to 6.5,the 50BMG proved to be too much of a task.
If your ordering bushings thier cheap buy them in .003 increments to avoid problems.
270wsm,7remag,30-o6,7mm mauser,6.5x55,708,22-250 and 223

So if you had 338 rum case and you were sizing it down to a 6.5mm you’d want bushing every .003 that would mean someone would need 27 bushings?
Could you go .020 every step? Will these cases need to be annealed too?
Thanks for your help.