Have you thought of using a roller? I use the foam rollers that are white and look like hot dogs. Saturate the roller well and roll out an area around 1.5 sq. ft. and then tip off with a 3 inch foam brush. Keep moving down the kayak rolling each area and then tipping off with foam brush by dragging the brush slowly and lightly from the dry area to the wet area overlappping your previous area an inch or so. Do not touch it again. It will level out on its own if you have applied enough varnish. It goes much faster than simply brushing, especially in hotter temperatures.