I don't know who needs to hear this, but you don't need to put hair care products on your synthetic hair. I know what you see in the videos. I know what your hairstylist did when you where in the chair...but I've been studying synthetic hair fibers for over six years and I'm here to tell you--you don't NEED it. Synthetic hair is not like human hair. Synthetic hair is simply a fiber and when you use your expensive (or cheap) oils, sprays, mouse, gel etc all it does it sit on top of the strand. It doesn't absorb into the hair because there is no hair shaft to open or close. So the itch that you may experience while wearing synthetic hair may not actually come from the hair itself--it's coming from all the product that is sitting on top of the hair or scalp and it's creating build up.
Anytime I wear a crochet or braid style, I never ever use any oils, gels or sprays on the hair directly. If anything I may take my water bottle and mist the hair so that I can finger detangle but I'll never grab a product to keep my synthetic hairstyles in tact. I also snip through any tangles or frizz throughout my style to ensure I have movement because who likes a stiff style. I have a video you can watch to see how I maintenance my hair (this method works with any crochet style).
There are two other things that make your style dull.
You keep putting your hand in your hair- I know it's touch to keep your hands out of your hair because it looks and feels so bomb. But every time you are putting your hands in your head you transfer the dirt and oils from our hands to your hand and you are stiffening the synthetic fiber. If you must put your hand in your head--wash your hands first.
You aren't covering your style- even if you are just laying around on the couch or laying back in your bed the friction between the fabric you are relaxing on is potentially drying out the synthetic hair. If possible, wrap with a satin scarf or bonnet or a satin pillow.
I hope this information helps. I want you to be well informed so that you can make the best hairstyling decisions so your style can thrive and have longevity.