Decided to go for it today and did the blackface mod to my Cobra head and cab. It came out really great, like it was factory. There are numerous pics of blackfaced heads, but none of a matching half stack. So, now there is.
Take off the knobs and emblems and lay the cab and head on their backs so the grilles are faced up. Spray it down with a healthy coat and wait about 10 minutes. It slowly turns black. Wipe off residual spray, then do a second coat on the lighter areas. I did a 3rd coat on some spots, basically until everything matched and was evenly black. Wipe down with a towel wet with warm water and install emblems and knobs.