For a 2-cycle engine there are several ways to make it work. The easiest is to use the reverse pitch prop. For an engine with a fixed front housing a reverse rotation crankshaft would be the next choice.

For a removable front housing engine(Enya), as Jen says, rotate the front 90 degrees left (from the front). If the engine has a rear intake, that would be 90 degrees right. Just make sure the intake opens as the piston is going up.

Swapping the front and back (per OS-FSR) would merely reverse the exhaust. For that engine just rotate the intake 90 degrees.

Using a reverse pitch prop is not the best choice since all model engines (AFAIK) have the thrust bearing surface between the front surface of the crank web and the crankcase (or crankshaft housing). Using a reverse pitch prop puts the load on the BB's or the thrust washer to crankcase surface (often separated by a washer).

George