Last year, the AP site had a link to sign-up as one of those crowd extras (so to speak!). The actual parade taping slots went very fast, but they had lots of other slots for the Castle Forecourt show and things like that. So, I was given an early Friday morning slot. We had to be there by 7:45, were split into groups. Then, walked up to the Castle, where we stood, in a sea of humanity, for an hour or so, before anything started happening. Then, Brian Setzer and his group came out...went over his number about 15 times. There was an arial camera on both sides of the crowd, but it didn't pass over us very often. I was in the third row from the front, and when I watched the actual show at home, I had to stop and start the show to actually see where I was, but did get a peek. I stood there for more than 3 hours, my back was starting to spasm, so I just left before any of the other acts came on...wish I had stayed for John O'Hurley though.
It gets jammed along Main St. but you can get through by going through the shops. The areas on the sidewalks are pretty much roped off, and those who were given the 'slots' are the people standing there, at least in the early hours of parade taping.
It really isn't hugely crowded in the attractions part of the park. I returned to MK later that afternoon and there were crowds around the special acts that were performing but that was it.
Would I do the taping again? Nope. I've done a huge amount of community theater work, as well as done a bit of 'extra' stuff in some films that have been shot in the area...so I do realize the amount of 'hurry up and wait' that goes on. But, there were a ton of kids that parents were shoving to the front of the groups, there was some 'interesting' behaviour during the long periods of nothing to do...I can't imagine doing it again with kids, or with my poor old aching back.
As far as being there when they tape the actual parade...it takes forever!! They'll run a float, or act, by, then send it back and do it again, and again, and again. There have been people that have thought being there for the parade taping was going to be a ball..just like they see on TV. But, they came back and had nothing but complaints about how slow it was. Guess they should have checked it out first!!!
Hope that answers some of your questions.