...BODY PANELS: Plastic media blast is the way to go, (or walnut shells, ...as mentioned above). But Plastic media blasting should be fairly available in most parts, ...it's not that expensive (roughly $300 to do a car) and it does an awsome job, (many places will come to you to do the job). I've been through this a number of times, ...with my own cars and with a shop I work at part time. What is 'neat' about it, is that it ISN'T harsh on the metal, ...actually leaves the metal surface 'clean'/smooth. The plastic media isn't abrasive and doesn't leave any residue, ...other than getting the vacuum out and cleaning up the stuff that blew around.
I wouldn't do it any other way...
...SUBFRAME: Depending on how bad it is,...you may want to conside sand blasting here. Once it's all cleaned up ready for coating, ...it depends on how much you want to spend. If not too tight on the budget, ...Powder coating is definitely an option (the results are awsome). Other than that, ...you may want to look into the POR products
http://www.por15.com/ , ...which are not bad themselves...
Kevin