How do you use fake tan on the face?

I am new to fake tanning and am going to a beach themed party quite soon. I recently bought a bottle of st moriz fake tan mousse which I have already tried on my legs (and it works just fine). However I've read about darkening pores and spot break outs on the face, and I'm not sure whether it's worth doing the fake tan on my body up to my neckline, then using darker foundation on my face. Or... if I should just use the fake tan on my face with adding a moisturiser. I know you can get special facial fake tan creams, but I as I am a poor student trying to save (st moriz was pretty cheap) and am conscious of facial tanning creams coming out a different colour/tone, I don't know what to do! Stopping at the neckline however isn't ideal either because once the foundation is off, I will have a tan line around my neck (and the tan lasts for a fair few days). Please help :) thanks