WD 40 is well known for rusting heck out of barrels, well known.
Blur, the generalization of cleaning with patches only and ending up in trouble with heavy carbon build-up, is not accurate due to the use of patches with JB, Iosso, Flitz Bore cleaner, Montana Extreme Copper cream, and JB(red)bore brite that can be used on patches with these mild abrasives.
The technique of wrapping a patch around a smaller caliber brush or worn brush is well known to clean the carbon out of stubborn carboned-up barrels.
A new product on the market is the Butches Twill patches, they clean more aggressively than standard flannel patches, but since the twill patches are thicker, you need to use smaller jags or brushes to use them with.
A couple of points I wanted to make, use of a bore scope will verify that your cleaning regiment is working for you, whatever it is. Second, the use of only patches and solvents will eventually leave a lot of carbon in the barrel if you do not monitor the build-up with a bore scope and remove the carbon with some of the excellent pastes available today.
This is just a hobby, and you take it to whatever level that peaks your interest.
Let me give you an example. I have a 308 with a very short freebore "Palma" chamber of sorts in a 28", 10T Krieger. The barrel has around 2000 rounds on it and still looks new in the throat. This barrel shoots the 169g, Sierra, touching the lands, with three different powders exceptionally well. At 200 yards, the barrel will shoot in the high 2's. At 300 yards, the barrel is shooting around 3/4", sometimes a tad smaller. Fast forward to after a 60-shot string on this particular barrel, and the groups are 3x larger. I am running a 10-50 Sightron III on the rig.
My 7 Mags are darn near exactly the same, but on 30 or so round intervals shooting IMR 4350 with 140's and Retumbo with 168s.
The 6 XC with H4350 seems to be the most forgiving, but the two 6 Dashers with H4895 are an absolute bitch to deal with concerning the carbon, and this cartridge has a 1400-round barrel life to the accuracy level I want to see, with the best accuracy in 1100 rounds..
I never worry about the copper as it is long gone prior to me dealing with the hard-cooked carbon.
Over the next few years, you will begin to see a lot of documentation on various cleaning methods in the Videos taken with the Teslong. I do expect to hear a lot of guys' testimonies on how they shot a lot better once they refined their cleaning regiment, verified by the bore scope.
Gun cleaning techniques are in their infant stages at this point which is accepted by shooters in general. The $89 dollar Teslong bore scope is going to change some attitudes as many learn that not having carbon in the barrel has a direct correlation to Accuracy.
You are always going to have guys that refuse to clean, and the other crowd that cleans whenever they lose accuracy. They are simply having fun with the hobby in their own way, nothing wrong with that.