The sealer was very easy to apply with a roller.  It is very much like applying thin syrup.  The difficulty I had was that my driveway had a lot of spalling and pitting and the roller cannot get the sealer into those pits easily.  I had to have a helper brush the sealer into those pitted areas then use the roller to paint over the area to make sure they are sealed.  After power washing and waiting 1 day to dry, I applied the 1st coat at 12:30 noon because I wanted to have enough time for it to dry.  The sun was strong but temp was around 80 so it was working fine.  Then the weather changed and I had to rush to apply 2nd coat at 10Am the following morning.  After application I started  seeing bubbling.  I think the sun was heating the sealer.  Despite the stray shower the next night the sealer appears to be holding up well. I busted the bubbles and there was dry sealer below so things worked out.  I no longer see concrete dust and the ugly pits are covered and sealed so I am happy.