Kona Lava Dome rebuild. Parts Question.

Hello All,
Just found out about retrobike and have been enjoying reading some of the build/rebuild threads.
I've recently been repairing and rebuilding my old Kona Lava Dome. I am close to the final assembly now and am looking forward to taking it out on its first ride.

I'm in need of a bit of advice as to what to do about some areas of the bike..?

Firstly, the rear brake and rear derailure cables run across the top tube of the frame. These were originally covered with a very thin clear plastic tube - a good, clean solution i think. However these tubes on my bake are becoing frayed and are full of grime. Does anyone know if i can get some similar tube? Or do i have to use the small rubber dougnuts?
Ideally I would like to use some tube again. Would any plastic tube be ok?

Also, as with most frames of this age there are a few chips and small dents. Should i treat these to prevent corrosion? I have considered sticking some frame protection strips over these areas like small plasters. Is this a good idea do people think?

Pics to follow.

Any advice would be kindly recived.
Cheers.

My local bike ship sells the tube off the reel. However a better solution is to buy a sealed cable system like Transfil Black Snake (or many others) which come in a kit with matched outers, inners cover tubing and ferrules.

Thats great. I'll look at a sealed system.
Thank you