Would this be a good alternative to applying the standard valve oil for valve slides for my horn?

Something like this http://www.performancelubricantsusa.com/product/non-stick-dry-film-lubricant.php

For your slides you should be using tuning slide grease. I just switched to a synthetic by ultrapure. It is extra heavy, and really lasts. My horns are 30 and 50 years old though, so you might want a medium.