I always chose to sand while watching something else and with some alcohol to make it more tolerable. Did the same when sanding old paint off aluminum and prepping the surface for paint which took hours. It is also what got me through sanding this very nasty but very hard deck back to the bare wood: 🖼 Pictures and Nothing Else! - #12433 by ApproachCautiously
It is titanium white which is already a very strong opaque pigment 
There is no need to add more of it to begin with.
As for being heavy duty, it doesn’t matter that much if the paint is coated in some other layer of protection. If you’re not sealing it in or coating it with a clear coat of some form, then it will matter since it needs to protect itself.
For comparison, my deck was painted with expensive acrylic paint (cobalt teal is not a cheap pigment) and then coated with a polyurathane clear coat to seal it in and protect it. Aside from me accidentally starting to strip part of it with alcohol, it holds up well to use. It can be dented slightly when installing the enclosures and trucks but it isn’t an issue since you don’t see it when in use. Kind of a pain in the ass to clean though