For coating my canvas (I've settled on Fredrix 7777), I use ClearShield Canvas Guard Type C Semi-Gloss and apply it with a foam paint roller. The coating protects the pigments, adds UV/moisture protection (it's considered a liquid-laminate) and makes the image "pop." The coating also seems to add some kind of elastifier to help during later stretching if needed and makes the surface less susceptible to scuffing, scratching and much more durable than uncoated.
The ClearShield is available in gloss to mat finish and I think there's maybe five different finishes available.
So far, I haven't seen any problems with the coatings once the canvas is stretched, even after nearly ten years since I started doing this.
I used to set up a trough and rollers when I had a several-hundred print project but now I'm only printing a few each month at the most.
It's faster and easier to set-up and clean up using a covered table and the roller system. One trick I did figure out, though, was to dilute the ClearShield by adding about 20-25% water to thing out the coating.
For smaller prints, up to a 16x20 wrap, I may get lucky and only need to make a single coat. However, I always figure it will take two coats. A couple of weeks ago, several 24x60 inch pieces did take two coats which can be easily done during a single day.
What I do is to soak the roller in a paint tray then squeeze the coating back into the tray. The first coat I try to even out over the entire canvas with overlapping strokes every which way to even out the coating. The first coating seems to leave visible streaks after it soaks into the canvas.
Once the first coat is dry to the touch which depending upon the temperature can take as little as a half hour and up to two or three when its colder like now, a second and thinner coat can be quickly applied which seems to make the surface of the canvas just about perfect.
I'm not certain that canvas really needs to be coated on the back since the ink and pigments seem to have some protection from not only the material but also the substrates and base surfaces of the coatings. It would be a very harsh environment that would require such efforts IMO.