Diesel fuel leaked out of tank onto paint/bumper guard

[HuskyMan]

OK, I was stupid and left a bottle of diesel additive draining into the fuel tank and forgot about it and drove off. When I turned left, diesel fuel spilled out onto the paint and the right bumper guard (the black part). When discovered I immediately took it to a super car wash and washed it.

Then, when I got home I sprayed the area with Simple Green and let it soak in, then rinsed. Sprayed it again and scrubbed both the paint and the bumper guard with a soft scrubbee, then let it sit a while and rinsed again. Is there anything else that I can do to dissolve the oily diesel fuel?