I filled it with 150psi of nitrogen. I stopped by my old work, they build pressure switchs, so they have large high pressure nitrogen tanks I used to fill it.
I did use alcohol to clean it. Perhaps there are better options, but after I had it thoroughly flushed I used a vacuum pump to evaporate out any remaining alcohol.
The dampening was good. It's now about 12K miles later. 10k of that was riding cross country and back. The bike is drastically different than it's stock form, but I can not really say if the 10 weight oil was better or worse than 5wt.
2011 Sprint GT, 2000 Moto Guzzi Jackal, 1981 Honda CB750F, 1957 BSA Bantam D3 restoration project, Past bikes -2008 Kawasaki KLR650, 1986 Honda Shadow VT1100C, 1998 Honda Shadow Aero VT1100C3, 2006 Yamaha FZ6, 2006 Kawasaki ZX-14,1980 Yamaha XT500