TECMike,
I have used Proguard. From what I have read Hengs is easier to apply, but I do not have first hand experience with it.
In 2015 I applied Proguard for the first time. Due to weather conditions I ended up rushing the job and it made for a long day (clean, dry, mask, cut, roll). I also ended up with some spots a little too thick (the higher humidity and finishing late in the day did not help).
Anyway, after 5 years it was getting thin and I went with Proguard again because I was familiar with using it. So last August I split the job into 3 days and that made it easy. This is for a trailer where the roof is 26' long & about 8' wide.
Day 1 - Cleaned it well and took care of masking.
Day 2 - Opened a 1 gallon can and took care of the edges which extend down side of trailer 1/2 inch. Cut around all vents, skylights, AC and then used remaining to cover front couple of feet of trailer. Did not cut in around ladder where I get on and off.
Day 3 - Rolled the rest of the trailer. Had it marked in 45' sections and would apply 1 gallon per 45 sq ft.
This was done on 80 degree days when working with material I would start at around 9:30am and finish by around 11:00am before it really got too warm. No issues with pot life.
By splitting into three days it made it easy, no rush, and felt like it did a nice job covering and expect minimum 5 years out of this and perhaps more because I think I spread it more evenly. Once this is on it really does appear to be quality material.
Hope this is of some help.
Take it easy,
Stu