I am not sure if this is what you are talking about but I have read when Brachycentrus caddis are around "anglers will brighten their tippet with white grease pen (Mean Streak brand) or typewriter correcting tape when fishing a Brachycentrus imitation" http://www.flyline.com/entomology/brachycentrus/
I have never tried this but I have heard about this from more than one person
There are two techniques that MAY be what you are referring to. One is when you are fishing an emerger and you want it to sink just below the water's surface. You can grease the tippet (with floatant) to within a few inches of your fly. The floatant keeps the tippet floating while the fly floats just below the surface. Another technique is when you are fishing fast riffle water with a dry fly. If you grease the entire tippet with floatant, the tippet will float and will have less of a tendency to pull the dry fly down. Since the water's surface is broken, the floatant won't spook the fish. Again, I don't know if this is what you are referring to.
Jock Scott over a century ago, wrote of Greased Line fishing as performed by A.H.E. Wood to present a fly broadside to Salmon to entice the salmon to strike. This presentation is effective on pacific northwest steelhead.The name came from the greased braided silk lines used back in the day, which in fact has nothing to do with the technical parts of the presentation.
The presentation is used when deep line swing in not working. Make your initial presentation more upstream, at a 60-to-90 degree angle to the bank, followed by a mend or two designed to square the cast and allow the line to sink.Follow the line with your rid tip as it travels downstream, keeping just enough tension in the line to allow you to stay in touch with the fly, but not so much that it prevents the fly from getting deep.As the line moves below you and tension increases begin to slowly lead the fly towards your bank, mending if necessary in order to keep the fly broadside to the fish. Nowadays this technique, do to our many line options which they were not so fortunate to have in the past can use this very same technique to fish many depths. I hope this info from a steelhead bum has been helpful.
Look up AEH Wood, (aka Jock Scott), Greased Line Fishing. Also articles by Bill McMillian on steelheading. This is a method of dry fly line method of fly fishing using wet flies (usually employed with salmon and steelhead flys) in a drag free drift, then letting the fly swing at the end of the drift (thus having the fly rise at the end of the drift) - so you get the drag free drift for over half of the drift and then employ the swing - very effective - try it with a caddis poopah tan on Putah, very effective in tailouts of runs.