I agree 100 per cent with Brian.
The thing that concerns me with any sizing, lubing or preparation is that in any process (even just the additional handling of the pellets) there is potential for inconsistency or damage. If you make 99 pellets out of 100 fractionally better but make the the 100th a flyer.....
I've only ever shot pellets from the tin. Suitable batches of JSB Exact will consistently group well under 10 mm centre to centre at 50 yards. Even the large weight variation (8.2-8.7 ish) does not have any measurable affect on performance in my gun; the velocity stays the same with the heavy and light pellets it's just the power that varies; they all land in the same place.
I just finished second in the World FT championships, achieving the highest day score with 49 ex 50 on day 2. I also finished second at the 2011 world champs in Italy. The pure accuracy of the gun was not the problem in either case! Pellet prep entailed pealing red tape from tin.
There is a lot to learn in FT but I think pellet fiddling is a dead end!