harry- I noticed you use a mop when cleaning. They don't fit as tightly as a clothpatchover a jag so perhaps that's why you weren't getting to the corners of the grooves when clenaing. Range-wiping the bore and leaving it wet with +9 plus probably gave it time to soften the corner lube enough to allow that mop to pick it up.
Taylor, LB and I pretty much clean identically and don't get anything on the WD40 patch when pulling it out of the barrel. The patch comes out spotless. We pull the barrels from the stock and pump in just straight cold water or cold water with some dish soap in Taylor's case. No rust, no fuss with this method. I'm testing a product called Unival, a multy-purpose lube that is also a water displacer. It was cheaper than a can of WD40 and is a much better lube. It doesn't dry like WD40 however, which is either good or bad as your opinion may dictate. I don't know if it's available in a gallon can, but may find out. So far, I prefer it to WD40, but always have WD40 in the shop.
When finishing a stock, the stock finish is instantly removed from one's hands & especially True Oil by spraying the WD40 into one palm than 'washing' them with it, then wiping them off with a shop-rag. I then wash with soap and water. Apparently, WD40 is also good for spraying fish bait or lures,(where legal) as well as for 'neutralizing' hemeroids. Of either, I have no experience - YET.