According to Charles... styling products are hard to wash out because when water comes in contact with styling gunk “it congeals and acts as a barrier, so your shampoo can’t get in and break it up.” His solution is to apply shampoo directly to dry hair and THEN get in the shower to rinse it out. This way the styling gunk doesn’t have a chance to congeal and create that blockage. Therefore, your shampoo cleans your hair better. Isn’t that interesting?
It’s true that styling resins can swell up and form an outer layer that is hydrated which then slows the penetration of water to the inner layer. That’s especially true for some old school styling agents like PVP. It’s also true that modern styling polymers are very water resistant which is why you can’t wash them out very well with water alone.
I think this tip MAY help. The advantage is that it does put a higher relative concentration of surfactant in contact with the gunk that you want to wash away. But, there are there are two potential downsides. One is that some styling agents are more cationic and shampoos tend to be anionic which means they could form an insoluble complex.
The other issue is one of potential irritation. You’re putting a higher concentration of surfactant in direct contact with your skin which could make it more irritating. I don’t think this is a huge risk but it’s worth mentioning.
But the best thing is we don’t have to just speculate on this. You could easily do one of our half head tests to get to the bottom of it. Assuming you’ve styled your hair such that you have equal amounts of styling gunk on both sides you could just sort of split your hair down the middle and to one half apply shampoo first and on the other half don’t apply anything. Then get in the shower and wet your hair and apply shampoo to the other side. After washing and rinsing if you can’t tell a difference between the two sides then this method probably isn’t providing any benefit.