If it has a manual tranny you can simply put it in neutral and use a tow bar. The lubricant in manual trannys and differentials does not need to be cooled, is not pumped and used as a hydraulic fluid, or anything of the sort. It's simply drawn up by the turning gears to lubricate the parts inside, and will do so whether being towed or being driven by the engine.
If it's an automatic tranny, the problem is the tranny itself. Tranny fluid is pumped around for use as hydraulic fluid and for cooling. If the engine is not running, spinning the output shaft via the spinning wheels will not provide these functions. The best way to tow an automatic is to either disconnect the drivewheels from the tranny or to it with the drive wheels off the ground. You can rent a tow trailer and just put the whole car on it. That's preferable to putting the rear end on a dolly and towing it backwards, because you don;t have to worry about the steering.