Nic-A-Date Trial Run

You're off to a good start! On the '23 and '24 it looks like you may not have used enough N-a-D. Try to get an actual "mound" of the fluid on the shoulder/date area and then just sort of look through it as it works. Don't be afraid to leave it on for a while. To Kloccwork's comment, there's not much sense in doing the whole coin until and unless you establish it as a coin that you really want to bother restoring the whole thing. Starting with the date is best. If the date comes back well and the coin has a few other things going for it, like a mint mark and a reasonable amount of remaining detail, THEN you go for the whole thing. Re-treating the date area when you treat the rest of the coin will NOT produce any ill-effects.

You've put too much on only if it runs off of the shoulder onto the surrounding fields. Not all of them will restore. Some dates are notorious for not restoring well, others come back so well they seem to leap off at you. Sometimes slick coins come back strong and sometimes those that have a lot of detail remaining don't come back at all. It doesn't always make sense. If you get 70 to 75% of them back you're doing well.