In no particular order...
For all types of coating I tape the prints down on large pieces of foamcore, 100% taped on all four sides. For HVLP, I use 1" blue "low stick" tape from 3M. For rolling, regular 2" masking tape. For rolling the 2" gives a clean surface on which to reverse direction. Yes lots of extra work there in the tape department, but beyond cleanliness the canvas very slightly shrinks as it dries which yields a nice flat, undistorted print, an advantage to us Gator mounters. I always leave white borders, mainly for mounting purposes. I leave the prints taped up on the foamcore coating substrate until I'm ready to mount them, very convenient for handling and storage.
36 hours minimum before leaning anything against the coatings. Maybe 3 days before I would consider surface to surface contact between prints or rolling into a tube.
OK, I like to lay down a lot of coating when rolling, maybe up to twice as much as when spraying. For me, keeping the surface wet seems to solve a lot of problems. Problem #1 when coating occurs when parts of the print start going tacky before you've finished with the rest of the print which usually is a result of trying to transfer coating to the canvas via the roller. You gotta pour the coating on, then qickly spread it over the entire print. A nice wet surface also gives you a longer working window, that's it's big advantage. But don't use so much that you completely obscure the canvas weave when dry.
Various canvases have varying degrees of the pinhole problem. I have found after much experience that if I gently work the canvas long enough the coating will get to the point where it is tacky enough to fill in pinholes, but not so tacky that marks from the edge of the roller will not level out. This works better when there's a lot of coating, and not so well for thin coats. It's a relatively critical call, you just have to practice. Once a while I have gone back and rolled over a very tacky coating to kill sudden stealth pinholes, and I have usually gotten away with it.
An aside...if you do think you're going to wind up with edge marks in your coatings, one option is to have at it with a brush to introduce a multitude of artistic simulated brush marks. I did not say that.
Have to mention that I am rather impatient, don't want to spray or roll more than 1 coat. Multiple thin rolling sessions will also get you around the pinhole problem, however I personally am no longer young. For the record, if you chose to do multiple coats be careful of the grunge that builds up where you reverse roller direction, don't drag that stuff on to the print on the second session.
For HVLP one thick coat of 3:1 Glamour, 15ml per square foot. Mark the vertical extremes of the canvas in 4" sections. Set the metronome to 84 clicks per second. Back the needle out a lot, air valve to the max. Take a vertical swipe lasting exactly 5 clicks per 4 feet. When you've done all the 4" marks, go back and do the same interpolating BETWEEN the 4" marks. Watch your distance, watch your speed, and you'll be sorry if you hesitate. Use a brush to remove coating from the tape so it doesn't run onto the print, tape is much last absorbent than canvas. I am generally within a nonce of getting serious runs using this technique. Takes practice, buy oh my it's so sweet and so fast and the coatings really look great. Others will have to experiment to find their personal best parameters.
Hardcore HVLP artists can buy a 5000 gram digital scale on ebay for less than 20 bucks. I used to weigh my loaded gun before and after each of my two spraying passes to verify how much spray I had actually put down. Thanks to the metronome, was typically 240ml each pass when coating a 4 x 8 sheet full of canvas. A fully loaded Fuji spray gun weights 1950 grams, in case you're interested.
HVLP is the way to go, no doubt about it. I only roll on miserably cold days in the dead of winter when the shed is simply too cold to heat, and sometimes for tests.
A great art teacher I knew used to make students do at least 100 variations of each new technique as quickly as possible, that's what you need with canvas coating. Save those reject prints and just experiment free and easy. I promise you'll learn something.
