Here's my 2c....
1. About how many pairs of lights would you estimate a coating kit will cover?
Wow - it's not that simple, due to errors in application, using two coats, type/size of lens etc, how many you do (if you do a few together, you can mix more at once and waste less) I would ask OldBlue as he ONLY does HLR, so he would buy more and know better I guess
2. How long are you telling customers the coating typically lasts?
Again, tricky one. For me, I don't tell them anything unless they ask. I have faith in the Infinity product, I've never had one complaint since using it. But if they ask, I tell them that if they bought a new light, it would normally have a 1 year warranty with it - and it will last longer than that. They are always happy to hear that. Then you have dealer/used vehicles - they don't seem to care where I live, as they will sell them anyway.
3. Anyone simply hand sanding to avoid power source issues?
Short term gain, long term PAIN! Get a bad set of lights and you'll know, for dayyyyyys after! Plus, if the customer sees that it's "simply sanding" they assume there is very little skill to it and anyone can do it - then they will question the value of your service.
4. Anyone trying two or more coating for more durability?
Most cases I use two coats. The first coat "sinks in" and leaves a more matt finish than I desire. The second coat fills any minor scratches missed by the first and adds that hard gloss shine to it.
Have a wonderful day,
Pommy