The only thing I use ArmorAll on anymore is rubber pieces that I want to lubricate. I use it on the exhaust donuts.

I leave everything loose. I do not tighten any of the clamps until everything else is in place. That seems to allow a bit more flexability in getting the hangers in place.

I slip the donut onto the shaft of a screwdriver and position it on the hanger so I can stretch the donut and then slide it onto the hanger with my other hand. A little lube on the shaft of the screwdriver helps.

The muffler has one side that is easier to get on than the other in my experience but I can't remember which side that is...

Finally I grunt and groan like everyone else until I have them all in place and tighten the clamps. I don't tighten them enough to deform the pipes so that when I need to replace a single component I can get the system apart (relatively) easily.

As an aside I will throw out the fact that years ago I learned (the hard way) that any time you are working under a car looking up it is wise to wear safety glasses. Having someone with a medical degree remove iron oxide from your eye cancels the cost savings of replacing the exhaust system yourself.

Randy