For those passing through with a dirty car. For under $11, they thoroughly vacuumed the inside (but not the trunk) and washed the outside. For an additional $2, they put on a layer of sealer wax and left a mild scent (Hester chose jasmine). They also had some really nice candy for $1.
2068 Tapo St. If you take the Tapo Canyon Rd. exit, Tapo St. is parallel to Tapo Canyon Rd., one street over eastward (yes, the name similarity is a pain). Follow Tapo St. a few blocks south. It'll be on your left just before Los Angeles Ave.
Coming from afar, Amtrak is the best bet to be dropped off right in Simi Valley. The Coast Starlight and Pacific Surfliner both stop here. Make sure someone picks you up from the station unless you have a car parked there. There's nothing at all at the Simi station, and little close by.
From either the 5 or 405 freeways, take the 118 freeway going west. Takethe Rocky Peak exit and turn left, cross the freeway overpass and park on the side of the road.