Re: makeup issues
firstly, i think you are apply your makeup too heavily. there is no point unless you need that much coverage, which most people don't. it's better to start with a light hand and build it up.
the foundation may also be oxidising on you skin so it will turn darker some time after application.
as someone suggested, match yourself in daylight (get a friend to help out). the best way is to apply 2 or 3 different shades in vertical strips from your lower cheek to jawline. you will be able to tell which is the best match for your skin. if your foundation is oxidising, you can go one shade lighter. although it would be better to have your power a little lighter than you need rather than your foundation.
for application, it depends on the foundation and how much coverage you need. for liquid foundation the MAC 187 is great for giving sheer to medium coverage and making it look very smooth. for creme foundations that come in a compact, a flat foundation brush (and a light hand) is a good choice, rather than a sponge.
if you don't need too much coverage, i would suggest not applying foundation everywhere.
for example, i only apply liquid or creme foundation on my cheeks and chin. on top and everywhere else is either powder or powder foundation to even out the shade and look.
currently it's mac full coverage on cheeks and channel matt luminere on top and over the rest of the face. otherwise, studio fix powder on nose and forehead and select sheer pressed to finish (i'm nc30 but i use this in nc20 as a professional mua (tv/film) told me it oxidised a LOT, and yes, shortly after applying it, you wouldn't be able to tell that i applied a lighter powder).
a lot of it comes down to trial and error.