Not to go a different direction but u may wish to sand down the canvas a bit after you gesso. That would rid the support of any lumps and bumps. Then just take a damp cloth and get rid of the dust rather then another coat to avoid build-up. As for a brush I use a 2 inch brush from Sears. works great and costs 2 bucks.
If you think gesso is hard try using the oil primer.
I took the road less traveled and it has made all the difference. I then took another and another. Now I know why the Chinese curse reads "May you live in interesting times"
Just call me Bill.