Sid, guides wrapped with tread are still able to be moved quite easily, and this allows one to position the guides in a straight line with the tip top after wrapping. To prevent the guides from moving when fishing the treads need to be locked in place by binding it to the blank. This can be accomplished by adding finish, such as epoxy. Epoxy will wet and penetrate the tread and and cause the tread to become darker in appearance with some translucence. If you want to maintain the original color then CP is used, it also penetrates the tread and locks it to the blank, and when it dries the color is more similar to the uncoated tread. However, CP is not tough or durable and is susceptible to solvents (such as water), so epoxy is put on top of it. Epoxy gives glossiness and durability to the CP treated wrap without darkening the tread since it can no longer penetrate and wet the tread. Most builders use at least two coats of CP to make sure there are no places on the wrap where the epoxy can penetrate and darken the tread. So if you like the color of wrap to be darker with translucence use just epoxy, if you want a color similar to the original tread color use CP. NCP tread is treated with an agent which does not allow the epoxy to darken it, however the wrap appearance is quite flat and dull looking. The reason for filling the gap between the guide foot and the blank is to help lock the guide in place and prevents water and dirt from getting into this space which can cause the guide to corrode. Almost all of today's CPs and finishes are quite good, only experience will let you pick a personnel favorite. I have been building rods for 47 years and have tried most of the CPs and finishes available and still have a hard time picking a favorite.
Hope this helps.

I said the argument was controversial, so I won't really try to argue it. You might try an experiment both ways and come to your own conclusion.

Regarding the tunnels, I'm not sure the mechanism, but I expect that if you don't get CP down the tunnels, and the CP on top hasn't totally penetrated, then the epoxy goes up the tunnels, you might get a mottled look. Again, it is my opinion that this is important, but I have to admit I don't know everything. I do submit that logic would indicate that the surest way to avoid any mottling would be to expose all the thread to CP. There is nothing to lose by being sure of the tunnel area loading.

Sid

You've received some good advice. Here are additional thoughts and cautions.

The "tents" along side the guide feet can be and frequently are a problem. It is really important to get CP into the tent void else the spar or epoxy finish most certainly will find its way there and you'll have a mess. Remember that epoxy contains agents to help it penetrate the wraps and it will do its job of penetration relentlessly.

Secondly, wraps ought to be firm - not crush the blank tight - and pack the wraps no more than necessary. The CP will better penetrate the wraps when they are not so tight or tightly packed.

Using CP is like inviting the in-laws to Sunday lunch and discussing the political issues of the day. It's a high risk affair until you find a CP an technique that works and even then . . .

I want to clear about my earlier post. Perma Gloss works great on cp thread. It make cp pop. I failed to mention I epoxy over the perma gloss. Good luck MH

Thanks, Michael. I've also got some Permagloss in my shopping cart!