yeah it's a lot harder when it is not in the car because there's no good way to hold the block still to get a good turn on the bolt.
Impact is the way to go here.
If you can't borrow an impact, you might try bolting the flywheel and possibly clutch back onto the crankshaft and then looking to hold that from moving. Possibly making a bracket or two that go from the transmission mount bolts to the clutch bolts on the flywheel
for example, here's something I rigged up to stop the flywheel from moving while torquing it down:
The same could be done to hold it for the crank pully bolt, then you just gotta brace the engine from moving.