Thanks for the tips, we will see how this goes. I never thought about scraping it off... So, that is the next thing I will try. and then use paper towels to get the rest. I think I overestimated the amount of sludge and gunk I actually have to remove. It isn't quite as bad on the remaining parts.
The big job will be brushing off the loose rust. I went to the store today and looked at an angle grinder with this twisted metal brush that might go through the frame.
But it would defiantly remove the rust. It would cost $45 and make short work of it. So, if things don't go quick enough, I buy it to move the job forward. I went with the $4 cheap version that will attach to my drill. I just have to keep in mind that I don't have to strip it to bare metal like I do for the exterior panels...
I hope this will work. Steam sounds good, but I would rather get this done now until waiting until after it was all put together and drive over to a steam cleaning place. I bet they exist here though. And water blasting would make a mess, so I'm hoping to avoid it.