Poly brushes come in different stiffness ratings and most guys never bother checking the label before buying. A stiff 8 inch will chew up soft clay, but a soft 8 inch can work fine in a lot of flues if you let the brush do the work instead of forcing it. Sounds less like the size was the problem and more like the bristles were too stiff for what you were running.

Roofers who let you climb up and see the rot yourself before you commit are usually the honest ones. The ones padding the bill won't want you looking at anything. I always ask them to take pics of the bad spots, and if they get weird about it, that tells me plenty.

Been running a grease gun on my trailer hubs since around then too and the bearings have held up fine. The one thing that matters is getting enough grease in there, so I pump until I see old stuff push out past the seal, then wipe it clean. Too little grease is way worse than the method you use. Just check them by hand at every oil change and you will know if something feels off.