If simple green is used I’d use the newer aircraft simple green or at least the purple.

But I honestly wouldn’t use simple green at all. Fully disassemble, let sit for a few days in ATF, tsk routine once a day or so and rub rust with bronze wool or 0000 steel wool, then a full blast with non-chlorinated brake cleaner. Then heat the frame, cylinder, and ejector rod in oven at 200 degrees, take out, give it a one minute Oxpho bath, then follow the instructions on the Oxpho bottle. Properly lube then gun and reassemble.