Rear Axle Questions

95 Blazer, GT4 rear (3.73 gears), G80 positraction

I changed both rear axle seals and now need to tighten the pinion lock bolt. How do I clean the oil off the bolt and out of the hole that it goes in so I can apply Loctite? The bolt is too long to be removed without removing the diff. I was thinking of shooting brake cleaner through the hole. Is there a better way?

How do I measure the ring gear so I know which one I have? I could try wrapping a string around the gear, measure the circumference and then calculate the diameter. Just curious so I know which torque spec to use.

Thanks in advance.