I'm always amused reading questions on this topic. Most people receive more radiation walking about their daily activities than they get from their watches, camera lenses, or probably binoculars.
Good job. A couple of years ago I went with the sunlight route. It took almost two weeks to completely clear, but was well worth it, although my patience was wearing thin. If there is a next time, I think I'll try your method!
I've used Arista EDU 400 several times quite satisfactorily. As AJG mentioned, developing and printing/scanning your films is a great way to not only reduce costs but also to have complete control over the process and be able to adjust many factors.
Spotmatics are plentiful on Ebay, with and without lenses. Just do a search every couple of days to find one in good condition at an acceptable price. If you already have a Takumar lens, all the better.