I've always done it with the levers on the bike - remove the cable, put the spray hose in the cable hole and spray while shifting back and forth, then pull the brake lever forward and spray from above. The runoff drips out under the levers and doesn't touch the hoods. Once the levers are unstuck you can add triflow, I can't see any real advantage in waiting for them to dry, because any residual wd40 will simply act as a carrier.