Bum Blockades weren’t exceptionally common; however, we do know of a few instances. A quick google turns up [this] (https://www.legendsofamerica.com/ca-bumblockade/) website that briefly describes these occurrences. It seems to indicate that Bum Blockades were fairly common in the beginning, but that they rapidly disintegrated once the Federal Government got involved. In a previous post, here, I did mention and give the impression that they were the norm. That wasn’t the case after roughly 1936. That being said while the outright blockades ended, California law enforcement still tried to limit the influx of “Okies” and “Arkies” into the state in an attempt to stop a labor surplus that would cause wages to plummet. As to taking bribes or demanding to see money, anecdotally, I would not be surprised if this was the case, that being said I currently at hand do not have any sources at hand to back that up. I was an assistant instructor for an Intro to the American West Course last semester, I can try to ask the professor for additional sources for this, as this was something he mentioned as well. If I remember I will post an edit if I get anything else.

Edit: My links broke, trying to fix them fixed also additional source: Gary C. Anderson, Kathleen P. Chamberlain. 2007. Power and Promise: The Changing American West / Edition 1. Pearson.