On gasoline engines you really don't need a special smoke muffler, just a pressure nipple somewhere near the exhaust inlet for the smoke oil to flow into the muffler.
I used a J&A muffler on my BME 50. The J&A comes with a pressure fitting already installed. I tried a Perry smoke pump but couldn't get it to pump enough oil so I used a vacuum activated fuel pump for an outboard engine and it pumps great.
I drilled and tapped the BME engine case for the pressure fitting to the pump and used a smoke valve from Tower Hobbies on a servo for the smoke control.
I also mixed the servo for the smoke valve to my throttle servo in the radio so at low throttle settings the smoke valve would close some so it wouldn't shoot too much oil in the exhaust system.
Works great and at a fraction of the cost of the electric and some manual smoke systems out there on the market.