I, too, have an LG. This year I added a fan and replaced the thermometer/hygrometer because I broke the old one. Once I got that regulated, the whole setup has worked like a charm.
I incubate and hatch in cartons. I have sponges under the vent holes and add water that way. My temps vary between 100.0 and 100.8 BUT the key to keeping them that way is to watch the humidity. As long as I keep the humidity above 38% my temps are rock steady. When they start to rise, I generally find that the humidity is falling and if I add water, the temps steady right out. Knock on wood, I have not had to adjust the temps at all in the last 3 hatches until I hit day 18. Then when I up the humidity, I do generally have to touch the temp knob ever so slightly.
Oh, and the only time I open the bator is when I candle on day 7 and day 14. Then on day 18, I open, refill all the reservoirs, add additional sponges, candle, and shut 'er up until the hatch is over. I don't have a turner but I use a block under the bottom edge of one side of the unit and move it every 4 hours--for a total of 5 times a day--so that the eggs get "turned" that way. I stop this process on day 18 (the END of day 18).
I keep one vent open all through the incubation and the 2nd one open from day 18 forward.
I think the key to the whole process is to learn what works in your incubating spot and do it that way each and every time.
HTH
Rusty