Hello,
I think you can spray the sealer on Pump Up Garden Type Sprayers. If you are sealing over a previous failed finished you will need to remove the old finish first. Sodium Hydroxide Based Strippers will remove most oil stains and sealants (Delco's DSR-50). Testing is required with strength and dwell time because of the variation in the quality of the old sealant plus degradation due to time and weather. You need to use the stripper as weak as possible and you can increase dwell time by covering the stripper with plastic sheeting. It is not unusual when removing stains for it to take two or three cleanings.

Sprayed on sealer from a pump-type or any other type sprayer will still need to be 'back-rolled' with a roller to remove and spread excess overspray....

Close areas will still need to be hand brushed...

Save the wasteful 'spraying' step and simply roll and brush.

You'll save money and end up with a better finished product.

Roll and back-brush is the most effective method of adhesion and coverage.

Michael

just brush it. A 10x10 can be brushed with a 4" brush in about 45 minutes. A brush works the best

I just finished a deck and my research supports all the brush suggestions above. Also, go to the stain manufacturer's web site for cleaning and application steps. Be sure to wipe any excess that's still sitting after 20 or 30 mins or so, or you may end up with shiny patches. Don't apply in direct sun.