A man I have done a lot of work for ended up paying my to repair the damage done when the RV service place did a bad job of winterizing the prior fall.
He asked what I do. I explained the whole process. Then I walked him through his coach and we located the low point drains and some other problem spots. When he asked about "Red Pop" as it gets called locally. (A reference to a local soft drink.) I told him that that is only for drains in my view. Then I laughingly (I thought) told him that if he does the air blow out, but is unsure, he should put some food color in a gallon of cheap vodka and run that into the lines.
When we talked again (we was looking for a quote on a simple upgrade), he thanked me for showing how to winterize. I was a bit taken aback when he said it has been great, but the ice is bad and the coffee is strange until the "blue water" runs out....
If you haven't figured it out, I will leave you to think about it.
Matt