1. Most of all fights can be skipped. The only required fights are bosses, "kill all enemies areas" and valves that open doors (although those can often too be compleated without killing everyone).

2. Flamethrower is your best friend. It is the best waepon for basic enemies due to its infinite pierce, and decent time to kill on easy. It can also allow you to stun enemies, since basic enemies dont attack when they are on fire you can sometimes use the valve without killing all enemies in the area. but be caerfull, enemies dont count as dead untill they stop moving, so the running blackened enemies still count as alive for purpuse of delaying next wave in "kill all enemies" rooms.

3. From my experience basic shootgun seems to have the highest dps against most bosses, and is the fastest way to kill brutes (ogryns/meganobs/space marines) however i reccomend bolter rifle against space marines, since its easy for them to kill you up close if you are not caerfull about your hp.

4. Both dealing damage and recieving it fills your waaaah! meter. in that matter hp is a resource you should be converting into waaaah! energy as long as you dont die. becouse of that allowing yourself to be hit is often beneficial.

5. To maximise dps you should time waaaah! usage in such away to use it to reset overheat or instead of reload.

This guide will be updated with more tips as i find them.