I am the owner of fx guns with 3 smoothtwist X barrels. 177 .22, and .25 caliber. It usually requires some thousands of shots true the barrel, before cleaning is not that big of an issue. Some barrels takes longer time than others.You probably has to clean regulary the first tins, and then it will slowly last longer. Of the 3 I own, my .22 crown is the worst regarding fouling. I lubed pellets first with ballistol, which helped, but then I tried silicon oil, which really helped. It basically removed the problem. But I am not sure I can shoot with it unlubed yet. On my wildcat in .177 I shot unlubed pellets all from start, and probably cleaned first every 200-500 shots. After I did shot more than 10 tins with 500 pellets each, it hardly seemed to need cleaning at all. Been several thousands shots without cleaning so far. My .25 is still pretty new, so it foul some. On that barrel I also started lubing pellets with silicon oil after a couple of tins. I am on my 8 tin so far, and plan to not add more oil on the pads on the tin, and slowly let it shoot pellet less and less lubed, and see how it goes. Also the muzzle velocity might help. So if you have to clean very often from the start, you might try lowering the speed some, and see if that helps.
I would also recommend stick to JSB pellets, as some other brands have bigger skirt or head diameters which leave more lead deposit.
I usually clean with patch worm, and also add some ballistol on the first patch if the lead is hard to remove.
If you remove the barrel, or liner when you clean, you can see the fouling with naked eye usually at the end of the barrel near the choke, using a flashlight. So when I clean I always inspect visually before and after. If it all looks mirror smooth when shining a flashlight from breach end, it usually means there is no lead deposit.