I use this procedure... Initial investment ~ $100 (for sprayer - local HW store, , Lysol - amazon, and plastic plugs - local auto parts store) and works like a champ.
Now I do it 2x a year an X5 and other BMWs - mine and friends (I made holes for them and do it whenever they need - I am being the great guy, it takes 10 minutes and they always bring good beer ) - no smell at all.
Lysol- since it is concentrated was sold only in 4x1 gallon jugs and I thought that it will last me for 100 years but since wife found it as a great way to sanitize her kitchen working areas - in a year or so I will need another batch..