Resident Evil

An important feature in this game is having the Fuel Canteen, located in the East Wing save-room on the first floor. You need to fill the Canteen with Kerosene, where are large silver gas canisters. One is found in the save room with the canteen and you can load it up with "2" uses. 

Next you will require a lighter, Chris automatically has this in his inventory (top right slot, not inteferring with the other six) but Jill needs to obtain it from the study above this save-room. In order to access the study, go up the stairs and towards the white door on the right, then run down the hallway to another door. Exit into a U-shaped hallway and head to Jill's right for the final door on this end. The Lighter is on the large receptionist styled desk near the Botany Book.

Finally you will need a zombie. Insure that it is dead first as trying to light a downed zombie who hasn't bled out will simply force it to stand back up. Once a pool of blood has formed around their body or you had previously killed a zombie in another room, simply use the Canteen on them and you'll automatically light them up. 

Note: If the zombie's flesh is red, this means they are already a Crimson Head. Trying to light them will only force it to stand up. There is no point in lighting a dead Crimson's body either. Second note is that there are several bodies laying about the mansion that never get up and even disappear through progression of the game. These include - one laying in the Crow-Cage hallway, one outside of the Serum Save Room and one lying in the basement kitchen next to the elevator.