the problem is most carpet cleaners get their knowledge from companies trying to sell them stuff or from other carpet cleaners who are as inexperienced and are just repeating what they have read or heard..... like the 'hair shampoo, rinsing' analogy its total bollox but is regurgitated every time detergents are mentioned (just like the dirt will turn to mud if you don't vacuum)
we should all be students of the science of cleaning read every thing we can find from impartial sources, it sounds sad but I look at the ingredients of cleaning products and any chemical I don't know I search on google...... don't just use F90 but look at the ingredients and search them on google. find out how and why they work
most training courses don't teach why we use a product or how it works...... only which product to use