Proportional Reducer to retrieve negatives?

I messed up developing some 35mm rolls of Delta 400 - developed it for 18mins or so instead of the recommended 9 mins in stock (I thought I was using it at 1+3 for some reason). The resulting negatives are very dense and way to contrasty - the fact that many are night shots doesn't help. I can just about print them with exposure times about 1min to 2min printing at 5x7 at grade 0. But printing at 8x10 produces unacceptable grain.

So, I was wondering if it would be worth it to give these a shot with a reducer. The only place I could find any reference to these is Horenstein's Beyond Basic Photography and he mentions three different kinds - Subtractive, Proportional and Superproportional. I believe my negs were properly exposed in general - so I would need to go for a proportional reducer. However, I can't seem to find any online. Only Kodak's farmer's reducer is readily available.

Do you think it's worth giving it a shot? Will it improve the grain/density/contrast of the negatives? Any other alternative approaches?

Any help and advice would be greatly appreciated.
Thanks,
-A

This is a really good way to do what you need. Get some RA4 bleach fix. This is much more controllable than the common farmer's reducer. Take a length od say 4 negatives and put it into the reducer to test for the amount of time required. Time the operation do that you know how long it took. Once you have found your time you can put your film back on reels and reduce as required.

This works better than black magic.