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Hey everyone, I'm a technician at a music production school in London. As the most 'guitariest' technician on staff, I've become the de facto guitar maintenance person.

A big part of my work is taking a look at each guitar once a week.
Usually my "routine" is to check action and intonation, making adjustments if needed, then cleaning/polishing.

The thing I struggle with the most is getting strings feeling good. We use D'Addario 80/20 bronzes, I assume because they're fairly cheap and decent. I use nanowebs on my personal guitar, mostly because it stays friction-less for much longer than uncoated strings, but they're almost 3x the cost of the D'addarios.
We have some half-empty bottles of Fast Fret and Dunlop's ultraglide 65 which I've used but they never seem to do much. At best it feels like they add a not-great-feeling coat over the strings which lasts a few minutes and then leaves the strings feeling differently bad. Maybe it's because they're old bottles and the applicator fabric has been almost completely worn away.

In essence, I'm looking for some advice from you wisened folk on how to best perform regular maintenance on guitars like these. Any advice about keeping strings lively is particularly welcome!

For reference, we have ~4 Gibson/Epiphone acoustics, 2 Les Pauls, 2 Casinos, 2 viola basses, and a firebird bass.