Hi Jetmech, I think i had the same problem you are describing. I still haven't mastered those little hairs, but was given what has so far been some good tips, and am making progress. First of all, my finer hairs always seem to be in very sensitive areas. I have only been straight razor shaving since January... and cringe at the idea of going ATG in the corners of my mouth. I dont have a 'stache and have those fine little hairs left all around my mouth after my first pass. I tried all kinds of things (not ATG), and only accomplished epic razor burn in those areas. So now, i only hit those areas 2 times...then a light (very light) touch up if needed. What helped me was the suggestion to stretch the skin by opening my mouth very wide, yeah i had already done that with no success. What i hadn't done was use my tongue to apply a small amount of pressure from the inside of my mouth as i was holding my mouth open...thus stretching the skin, and making more of a straight surface for my razor to glide across. BE VERY CAREFUL, and only use a little bit of pressure untill you find that sweet spot. If you make the corners of your mouth or that patch under your bottom lip, stick out too far...well you will have less of those corners to worry about untill they grow back. This has helped me all around the troubled spots on my mouth, and i have less and less fine hairs left each time. So far i have kept all the skin too...I hope i didn't just jinx myself! So just stretch the skin however you can, no one will see the strange faces you make, while you are using your tongue to make those fine hairs easier to get to.
I hope this helps. I had just never thought of using my tongue to make things more flat. I havent given anyone advice before about straight razor shaving, I hope this is helpful. I really hope that your dont end up looking like The Joker, and post a pic in the cut of the day thread...blaming me for your deformity.