Hiya guys..kinda late to the party ( been with my boys all week

).
Chief..sounds like you might have had some bad mat. Got wet or something. You mentioned that there were some 'White spots' so it could have been wet at some point.
I never have any problem with brushing or rolling mat. As long as your not jamming the brush too hard you should have been ok. Sure sure..some mat tends to pull off, but not severe enough to warrant frustration. Dabbing is used for corners and spot wetting..but you can and should be able to lightly take brush strokes at it when moving resin around. But the roller nap is still the way to go for larger layups as already mentioned above.
A few points though. First..you may not want to use a power mixer when mixing resin. It will shorten your pot life ( sometimes dramatically ). Mixing a quart for 2 minutes is even a bit extreme. A few 20-30 seconds should be enough. This kinda goes with 'warming it up' scenario. Warming it up to thin it out will result in a reduced pot life as well. You could do it..but you better be prepared to work fast!
The bubble roller your talking about is for rolling out bubbles After a few layers have been wet out. The thing wont do you any good working with only One layer of mat..and is not meant for resin coating.
That MEK bottle is the bomb! A few things like storing mek and proper and fast measuring have already been said. But..here are a few more that might help you out. You might consider drilling a small 1/8" hole in the top. Right around the neck area. See..when the thing warms up a tad..the MEK will push up through the spout and into the cup..sometimes filling it completely. Then the next time you take a grab at it you have hardener slung all over you. Also..after a few mixes you wont really need to read those little numbers on the cup. You will be able to eyeball for the next quart etc. You could take a magic marker and mark where you would squirt for a quart. Need two quarts?..fill it twice to the mark etc.
Lastly..I suggest that you still use the mat even if your using 1708. I know I know...1708 has .8oz mat backing. I think thats enough for stacking them..but not for the primary layup. IMO..putting down the 1.5 oz mat first..then the 1708 mat side up works the best. It rolls out better and leaves a nice mat surface for you to scuff for your next lam..or to start prepping for topcoats/gelcoats.
Anyways..good to hear things are picking up for you..rock on man!