While people talk about smoke from their engines, it's really a function of the type of oil in the fuel, the amount of oil in the fuel, and the mixture setting on the engine. Some fuels will smoke a lot when the engine's properly-set, other fuels will not. You cannot rely on the amount of smoke exhausted to determine if your engine's properly-set. You must listen to it and/or tach it. You want the engine running rich of peak RPM.

Oil emitted from the exhaust port or pipe on the muffler can land on the model, and it's normal for the model to get quite a lot of fuel on it, depending upon the location of the exhaust outlet. Adding a diverter to the the outlet may reduce the oil on the model, but it may also induce overheating of the engine, because a diverter adds a little bit of back-pressure, and it can be just enough to encourage overheating. You can only find this out by trying the diverter.

Just carry rags or other types of wipes to remove the oil that accumulates on the model. If you fly glow, this is a normal thing.