Thought I'd pass along a few things I've done over the years in hopes of stimulating some discussion.
* To dye test something on the bottom of the pool, without diving, such as main drain, I duct tape a 1 oz. reagent bottle with dropper tip, full of dye, across the bottom of my tele pole, put it on the bottom by the suspect area and push on the pole to eject dye from the bottle. Works best on larger leaks - over 1" per day.
* When I locate liner leaks, I stick my syringe in the leak to mark it while I get a patch. Especially small holes/pinholes, you don't waste time re-finding the hole when you have a patch ready.
* I mix marble dust in epoxy to give it some texture and a better grip to the surface it's applied to.

i know you all have tricks of your own, please share.

I have been using your main drain trick for over 25 years but hadn't thought of the second one. Makes for a good, fast locator.