I did mine earlier this week.
I found that if you put the new key into the lock (with the lock out), you can see which tumblers (wafers) are correct and can stay in place.
I managed to re key my locks with the parts I had.
I was short of 2 No 1 wafers and had 2 No 3s spare.
This meant that the locks only have 5 working wafers in each.
(I hope that makes some sense).
Mike.