Biohazard tips?

Can you suggest me some tips to win BioHazard? I mean, i always reach the boss with 1 or even 2 lives,using some Hypomeds, but then i'm always alone or with 1 player and i can't even damage the boss until he reaches half life...

I'm a good ZM player, in Unearth i'm good but it's too easy due to the large space of the map, but Biohazard is hard and i can't use my minimi/m60 adv , but only noob guns.

Give me some advices to win the boss, because :

1)200 times won UnEarth, never got minimi/dual de/fn

2) 4 times reached the boss, once with gold crate and 3 with silver one, got kris,kris,kris and fn2000...