I have interview with Gibson in an issue of Darkroom Photography from 1989. At that time he was still shooting exclusively Trix and rating it anywhere from 100 to 1000 depending on the subject matter, developing it in Rodinal 1-25. He was using Agfa graded paper and usually printed on grade 3 or 4. He controlled contrast further by varying the dilution and development time in dektol.
One interesting thing was he used a hardener in the fixer because he said he liked the surface it gave the final print.
Another interesting tidbit from the article is that the enlarger he was using at the time was the same Leitz Focomat 1-C that Robert Frank used to print The Americans
Today he still shoots film with a Lieca, (heck, Lieca has a designer MP with his name on it for sale in a limited edition @ $4800) but I think he has moved more and more to printing inkjets.