I used this product and started by brushing in all the edges and corners with a natural bristle brush a few inches out then used a synthetic applicator pad on a screw in stick for everything else

I used a drum sander with 20 grit i suggest you use 36 grit though to avoid sanding marks

I learned the hard way to remove the original coating and then sanded with a 3 head random orbital with 50 and then finishing with 80 grit