Ok here is an update on the test piece for the deck restore.
One coat using a regular paint brush

later that day I did a second coat still using the same regular paint brush(but forgot to get a pic

)
this is after two weeks (12 days is that close enough to call 2 weeks lol) It has been sitting in the elements the entire time, rain, heat, bugs lol


Is holding up very well didn't bust along the seams.
this is how smooth I was able to get it with the brush on both coats


And here is how it looks on my ttt

TJinPgh,
To answer your question about "their technique" I personally would not use that roller again,
1. to get the product to transfer from roller to surface takes a lot of pressure, It wanted to slide across the surface.
2. uses a tremendous amount of product
3. very hard to get into tight places (have to end up using a brush) and doesn't look the same.
As far as I can see with the foam roller Idea as long as it was the second coat It would probably work good, the problem with rolling is if the roller slides the least little bit, It wants to push the sand around and leave you with "flat spots"
Now with that being said, the product itself seems to be great with a brush. I don't really see that much reason to thin it out, At least in my case because I wanted a thick coat of "armor" so to speak. But thinning could maybe get a slightly smoother finish but would need more coats. (think the benefits would be very minimal )
Another bonus of it, is that it seems to be an added conversation topic for people. Everybody wanted to know If I stuccoed it LOL I told them Yes It is built out of cinder blocks and stuccoed

They all looked at me with this bewildered look on their faces

and my grin gave me up everytime!
The luan I used was just the el cheapy stuff from lowes.
The sides went as easily as the top surface! It's not so thick you cant move it and not so thin it runs.