for making the garbage disposal not stinky, a) make sure you use a lot of warm/hot water when you run it - and keep the water running for a few moments after you turn off the motor. that helps wash down all the bits and b) i tend to scrub my whole sink out with baking soda every couple months and just rinse it all down the drain. baking soda is glorious for eating up smells.

I use the little packets for our dishwasher all the time! I love them, so much easier than powder or gel. the ones we get are all one sealed packet, but seem to have two "sides" - a grey/white side and a green & blue side. i just make sure i put it in the little door with the grey side down and it seems to do a great job.