I did my boom over the winter.
I sanded the old black paint down to bare aluminum with 100, 150, then 220 grit with a random orbit sander. That went quickly enough and cleaned up all the imperfections. My mast and boom are also Kenyon.I also used Interlux but I went with the 2-part primer and 2-part finish coats called Perfection (I think).First, I used one coat of bare metal primer by rustoleum (make sure it is for oil based paint). I put two coats of the 2-part primer and 4 coats of the 2-part Perfection. I used a 1" brush. I wet sanded lightly between coats with 300 grit. The 2-part paints are expensive and a real PIA to work with and clean. I had to clean the brush with acetone between coats. When I got down to the last 2 coats I did only one side at a time to eliminate any kind of imperfection where the boom was resting. If you could hang it up with dowels at the ends I suppose that would help.I think one pint of primer and Perfection is enough to do the mast and boom. The boom turned out so well that I am looking forward to doing the mast this winter (I didn't want to drop it last winter, but I will this year for sure).I did the boom indoors and I can get the mast in my basement also, so I will do it indoors as well.