Does soaking feet in warm water with salt help in detoxification?

Yes

I don't think it really matters on the detoxification process but most widely know detoxification for feet is foot spa. This may include pedicure, manicure, and foot massage. You can go for some known spa venues. If you are in the UK, you will know some perfect destination for detox on the following URL :

http://www.spaandpampering.com/