If you guessed that head and cylinder prep meant more time at the blast cabinet, then give yourself a gold star! I lucked out and got a pair of cylinders that were in great condition with no broken fins and only bored out to .005" and .010". They will be bored and fitted with .020" over-sized pistons by the machine shop, but before being sent off they needed to be cleaned and repainted. This was a very straightforward, but also extremely time consuming. Getting all the old hi-temp paint out of the cooling fins was a tedious process. I used the same blasting media as before, a fine grit aluminum oxide, slowly working over the fins from different angles.
My heads were not as pristine as the cylinders and required a more aggressive approach. It is common for head fins to be broken on flathead engines due to improper tools being used to remove the head bolts. A good wrench slip, on a head bolt, as snapped off many a cooling fin. Replacement fins can be welded in place and if you want to go that route, I'd recommend sending them to Faber Cycle for a professional repair.
Since the fin damage on my heads was relatively minor, I decided to just use a die grinder to smooth out the rough edges. Once they are painted black, everything should blend together visually.
Next the heads went through the blast cabinet to clean off all the old paint and rust. Once complete, all the parts were sprayed with an aircraft primer.
The results look more like what you'd expect for WLA parts, but they will be top coated black before installation.