For example, I’m looking for a clear shampoo with guar hydroxypropyltrimonium chloride. Any tips on how to find shampoos with this ingredient without having to sift through tons of products?
You could use the EWG’s data base. You can search by ingredient and then see which products use it. You still have to sift through a lot of search results (over 500 in this case) and the data base is not 100% accurate but you may find it helpful.