baking soda should be ok. you can also do a double or triple concentrated extended soak in star san after a blc cleaning. this would be for the faucet, dissasembled and soaked in these solutions.
for the keg, i would do a hot overnight soak in PBW, then replace the o-rings, and do another overnight soak in pbw. i would think that would get rid of the smell, and also make your keg extremely clean.
i personally just have a dedicated root beer keg (i also have 32 usable kegs though, so it is a bit easier)