How do you know if a product is working or not?

Yeayeah

How do you guys tell if a product works or not? I put in a curling enchancing cream in my hair and the white stuff will not rub out and it just ends up making my hair look nappy and my curls messed up. Same thing with the curing custard from cantu it's clear but it messes up my hair. I even use a little bit and it still leaves the white stuff and manages to mess up my hair. Am I applying it wrong or it doesn't work? I have 3c/4a hair