Since the S&S ECU won't allow the engine to fire up when cranking with the throttle open you could try cranking the engine over for a few seconds with it fully open. This should mean next to no vacuum trying to draw oil up from the crankcase while the oil is scavenged from the sump.
That's the theory...I didn't think to try it till after I had changed to a different ECU that would probably instantly have it bouncing off the rev limiter.
You don't really want to block any of the crank case breather hoses as a rise in pressure might blow out the crankshaft oil seals if you forget to unblock them.
