I took Jay's suggestion and started a more scientific test.  I took an aluminum can, a stainless steel chain plate, and a length of PVC pipe.  I coated half of each with Never Wet, and put it all in the water.   

The collage picture shows the early results.  Lower right with masking tape so you can see the coated and bare parts. Upper right zero weeks.  Left after one week.  Barnacles are apparent already At least one barnacle located on the coated part of the aluminum.  The bare parts are glossy, the coated parts are matte.  You may need to scroll left-right to see the whole picture.

I'll post again after a month.

I also learned something new about my prop.  Last month the diver said that he never saw such a clean prop, but he scraped it anyhow.   This month, I can see the places where he scraped; stuff is growing there already.

Therefore, 4000-5000 nm of motoring did not diminish the effectiveness of the coating, but 4-5 seconds with a stiff brush or scraper will destroy it.

Yes Jay, it is the two part version I used.

Below are pictures of the test result after 6 weeks.  

• The aluminum can portion of the test broke off and is gone.
  
  
• The test rig picked up more than 5 pounds of growth in 6 weeks. (Holy s***!) Looking at the first picture, it seems that growth was everywhere, Never Wet as well as untreated.
  
  
  
• I rubbed it with bare hands.  Almost all the growth wiped off easily on the Never Wet portions. Very little came off the untreated portions. Spinning your prop at cruising speed might be similar to rubbing it with bare hands. I learned not to scrape with a tool; that scrapes off the Never Wet too.  See the second picture.
  
  
• Although a bit of growth remained on the Never Wet portion, there were zero barnacles on that part.  Barnacles are the worst problem here.
  
  
• The Never Wet seemed equally effective on the stainless test as well as the PVC pipe test.
  
  
• The test rig is still in the water.  I'll take pictures again in a month or so. 

Sonic?  Never heard of that.  

I sprayed only the prop.  I also roughed up the prop surface with 200 grit sandpaper first.  Usually, one polishes the prop as smooth as possible.  In this case i roughened it slightly.

I also put on two coats, following Never Wet's instructions.  

Good luck