That's funny; the Ctrl+F text search doesn't find any mention of Slip2000 CK before my post. I only see KG-1.
The CK instructions say a 5-15 minute submerged soak for best results. The 2-5 minutes range is for when you apply thinly by rag to prevent, as you say, having it dry out. For a barrel, I just keep a bag of silicone stoppers, plug the bottom end, fill it, and let it soak for 15 minutes. May repeat if needed. Getting very hard old caked carbon of the space behind the piston head of a Garand operating rod one time, after two 15-minute soaks hadn't penetrated very far, I gave it a couple of hours. That worked, and the steel was fine, but it did start thinning the Parkerizing on the carbon steel tube (the piston head is stainless). Anyway, as long as it isn't on any applied finish, you can soak for quite a while.
The CK instructions say a 5-15 minute submerged soak for best results. The 2-5 minutes range is for when you apply thinly by rag to prevent, as you say, having it dry out. For a barrel, I just keep a bag of silicone stoppers, plug the bottom end, fill it, and let it soak for 15 minutes. May repeat if needed. Getting very hard old caked carbon of the space behind the piston head of a Garand operating rod one time, after two 15-minute soaks hadn't penetrated very far, I gave it a couple of hours. That worked, and the steel was fine, but it did start thinning the Parkerizing on the carbon steel tube (the piston head is stainless). Anyway, as long as it isn't on any applied finish, you can soak for quite a while.