Back about 50 years ago, when driving these things was common, it was a regular practice to prop a stick between the brake pedal and the seat to keep pressure on the brakes. It does tend to keep the cylinder cups spread out tight against the bores and prevent cylinder leakiage. Fortunately, old guys then would share secrets with new drivers.
Ah, yes, I remember. it was a first series 49 P-15 I got for $35. Had about 90,000 miles on it and was pretty tired. An old guy I worked with at the time was a Chrysler employee in the 20's and knew all sorts of oddities. Like the '30 Chrysler "6" I had was actually a '30 Plymouth with a different radiator shell. Man, I wish he was around now,,,,,,,,,,,,,.