I absolutely LOVE my Patchworm kit and use it on every one of my airguns, (Springer, PCP, multi-pump... I use it in 177 and a collar adapts it for 22.) I have also used the weed wacker strings and other things mentioned above. Most worked very well. (There are a lot of good ways to clean airguns.) But the best results FOR ME have been using the Patchworm.
I first run it through with one of their felt pads dabbed in a cleaning solvent. (I often use Balistol. Make sure it's something safe for the seals.) The pad is not dripping wet, just enough to get the solvent in the barrel. Then I wait a moment for the solvent to work, then give it a few pulls through with dry patches. I will repeat this as needed. I usually have a really clean barrel in minutes.
I did this last month with a new in the box P15 and was clean in 2 felts and about 8 patches. It took about 10 minutes.