I am a great fan of using washes to paint things up quickly, which can be very handy with 'nids if you are having to paint millions of little gribblies.
I'd get a good white primer, then decide what kind of colours I wanted to go for... generally either something where the flesh and armour are similar colours (like brown and tan), or very accenting (like tan and blue). Depending on the colours you go for, use an appropriate wash, or water down an appropriate colour paint, then hit it with a wash just to bring the details into relief a little.
I've seen a few people use glow in the dark paint on minis, but it tends to be quite thick from what I have seen and obscures details. It can also have a very paint resistant surface which it is hard to then paint over with other details.
If you want ideas for schemes, check out
this online painter as it has a random colours button.