I'd say there is a good chance you're getting the taste from scents in the Napisan. The best ones to use are the no-name brands, the ones that contain 346g/Kg of sodium percarbonate. Everything else has enzymes and fragrances. As said above, after using this stuff you need to rinse the hell out of it to remove all traces. It is used to remove all the organic matter left after fermentation. Follow up with a sanitiser.
Iodophor is easy to use. As you say, mix it up to working solution, spray or splash onto every part of your gear then let drip dry. I usually sanitise the laundry tub and let it drip upside down in there.
b_thomas, PSR is not odourless. It is a chlorine based cleaner. Although it doesn't stink as much as bleach, it smells. Dry and avoid inhaling it.