The only color preserver I have on hand is the Flex Coat water base. Is this OK to use on a rod that will be finished with glossy spar varnish?

i have found that olympic water based urothane works very well under spar varnish. it takes about two coats and you need to make sure the wrap is completely sealed at the guide tunnels. the urethane itself will darken the wrap about one shade on a 10 point step tablet. not much. you want to get a good flood coat on your first coat so thin it 25% with water. follow that with a full strength second or third coat. i apply my varnish with a toothpick or spatula and don't use a dip tube so i cannot comment on what will happen in a dip tube. test, test, test! use the butt of the blank where it will be under the reel seat as your test bed. light blanks are of course easier than dark ones. make sure your wraps are burnished well and also packed to avoid uneaven penitration. as to the type of urethane i think many of the water based urethanes will work. this is not to say that flex coat won't work either. test.

Most all CPs will work under varnish, but you MUST do a test wrap, as Larry says. I have blown many a wrap because I just knew the CP would work. Sometimes the thread color is critical. Are you going to dunk the rod? I find that Tru-oil rubbed on works just as well, with less build-up.

Not dunking. Just replacing one guide that was damaged. It is difficult to match the thread color because of the age of the other wraps.