In a previous thread there was a pic of a P47 covered in oil. There was the perfect set up for doing a form approach or landing. Guy could slid his canopy back but stay behind vice sticking his head out into the oil caked slipstream.
If that was Johnson's ship, he was partially blinded by hydraulic fluid on the initial bounce plus instruments had been obliterated by a 20mm cannon shell.
The canopy had been jammed shut by damage. But since the plexiglass had been blown out, he was able to look.
This is the P47 shot I was referencing earlier. If you look, he is covered in oil, at least from the shoulders out. I assume the reason you don't see his helmet and goggles is they were covered in oil as well...