Don't sweat the shower, tooth care stuff. There is a lot of hype surrounding scent elimination. I have been at this since 1962. I have tried a lot of products, and/or been around many others who have tried it all. Bottom line is simple. Stay upwind if at all possible. If a deer gets down wind, you are done. I'd suggest that you try to stay as neutral as practical. No need to stink ... the use of scent free body soaps, laundry stuff, topical sprays, etc. probably help. But do not think that anything will totally eliminate scent.
As far as what to use in a spin feeder? Most folks use corn only. Corn is only about 7% protien and can interfere with the natural digestive system of deer .... not sure about oats. If where you are setting this up, the weather is relatively dry, try some "deer pellets". More expensive than corn, but better for the deer. Also might try 50-50 corn and feed soy bean mix. We used to feed deer in "free" feeders. They loved the 50-50 mix .... but so did coons, crows, turkeys, squirrels, etc. So we quit that after about 10 years. We do not use spin feeders at all now, opting for year round food plots.