A layer of the heavy duty thick sound blocking foam was placed over the rest of the floor and laminate was put on top.

They are waterproof protectors and are nice and thick.

I also added an insulator below my hard vinyl flooring. which was sort a super thick vinyl and carpet padding.

Say the interior walls are about 6" thick. 

@Erik Browningyeah, maybe it was a bit "thick." 

If tile was laid down after flange was installed use an extra thick one.

I DON'T recommend the drop and lock system as a rule because you can't repair them as easily as the 2G or 4G locking systems.NEVER  buy a floating floor less than 4mm thick(not including the attached cushion).

I'm kind of disheartened to see nobody mention that the thick profit margins lay between what's mortgageable and what is not mortgageable.

Thick paint will clog and ruin sanding belts very quickly.Take some time to practice with the drum sander on a piece of plywood. 

It takes thick skin and a willingness to learn to pursue this full time.