OCW is a nice wax. Easy and simple to use. Use it monthly and it will do just fine. If you are looking for something to spot clean those specific things I would look into Opti-Clean (waterless wash), Instant Detailer or on those rare occasions Power Clean. Just be sure to follow up with some protection after power clean as it would degrade the protection on the surface.
Optimum No Rinse (ONR) would be good to have as well.
As far as claying, clay when you think it is time for that. People often refer to the baggie test. Google if you are not aware of that method. I would probably stick with clay rather than the clay towel as the towel has the potential to marr more than a clay bar.