Easy, take the baffle down while the stove is cool, stick your smartphone into the stove and take video of the inside of the liner, then play back and you can see build up from the bottom. Now having said that most of your build up will be on the top as the bottom runs hot so you would still want to sweep or visually check the top.
As for bottom up cleaning check out the sooteater I mentioned ealier: http://gardusinc.com/sooteater.html
I haven't mentioned it yet with everything else going on, but I would recommend insulating the liner (yes more cost), always a good thing to do that as it helps draft and helps reduce creosote buildup.
Cool, thanks for that explanation. I was thinking about getting one of those snake camera contraptions. Father in-law has one that I can borrow. I'll compare the two options and see which one works best.
Definitely getting that sooteater. Kind of nice to have all the info I need right here in one thread.
Yep, going to do the liner insulation as well. May as well spend a little more to make everything optimal