I clean mine every two tins (1,000 pellets) or earlier if using Accupells.
To clean it, I use 30 Lbs breaking strain fishing line, about 5 feet will do and tie a small loop at one end. In the loop I attach two small strips of jay cloth or similar (not a new one as her indoors will be asking why her new kitchen cloths have holes in them) which I "dampen" not soak in a mixture of gun lube/oil silicon basd stuff and a drop or two of pellet lube.
Feed the line down through the barrel which is easy as 30 lbs line is very stiff, and pull this through a couple of times. Then replace the jay cloth with new pieces which are dry and pull them through. Result, nice clean barrel and very tight grouping.
AA 410k, 3-9X50
FN19 Hawke, 6-18x44
AA S200, 6-24X50
S10, 8-32X50