An older engine would be even less likely to fire from a resting position, simply because
the comperssion will leak down after it has been stopped for a minute. A cylinder with no
compression will not fire at rest ever.
Just because an engine has leaked down does not mean there is not enough fuel air mixture to turn the engine over. Even a leaked down combustion chamber is enough to cause the engine to turn over past the next firing over, and thus start.
Here's a factoid for those keeping score at home....a magneto has to be spun over rather briskly
for it to produce any spark. First the magnets have to spin around the field coils fast enough to
produce enough current to then supply the secondary windings enough current to produce a
spark of 20,000 volts or so to the apark plugs.
Trust me, this does not happen by "leaning against a propeller".
Anyone who has spent any time working on planes and expecially hand proping older planes or even modern ones with dead batteries, then you know that just when you get the cylinder past top dead center you hear a click with a metallic sound, sorta like "tic, poing". This is the implulse coupler going off. When the engine is not turning the advance weights are retracted and a ratchet engages a spring, the spring winds up till it meets a point just past top dead center where it is released and momentarily spins the magneto fast enought to create a spark. After that the magneto snaps back to its original point and then fires at its normal advanced rate. But the point is that the engine does not have to be turning fast, because the impulse coupling spins the magneto.