Yeah, you can clean up the engine or use a trace dye and UV lamp.

OR degrease the motor,
Get an aerosol powder, such as that used to treat athlete's foot, and spray the underside of the general area of the leak.

The powder will adhere to and coat the metal, producing a white haze. Then, drive the vehicle until the oil leaks--be careful to avoid wet, muddy roads in the process. The hope here is that the leak will take a single large, reasonably direct downward path (even if there are some streaks from airflow).