The Demolitions perk is designed as crowd control. This person will be dealing massive amounts of damage to large groups of zeds at once using his grenade launcher or RPG.

The main downside to this perk however is that it suffers in close combat, as you can hurt yourself with the explosion of your weapon, or the rocket/grenade will not detonate at all.

Here are a list of tips in order to succeed as the Demolitions perk.

1. Stay with your group - Since the Demo perk falters at close combat, let your teammates pick off enemies that are close so you don't have to.

2. Keep your distance - Despite explosive damage resistance, you can still be hurt by your own explosives. Rockets and grenades will not detonate if they are shot too close to the enemy. So make sure to stay at a safe distance as well as being in the proximity of your team.

3. Don't waste too much of your ammo on Scrakes - Scrakes have 50% explosive damage resistance, so don't blindy shoot them. Shooting Scrakes will also enrage them, putting you and your team in danger. Let a good Berserker deal with it. On a side note, Scrakes take 50% extra IMPACT damage form RPG rounds, combined with extra damage from headshots. So if you must, fire an RPG to a Scrake's head for good damage.

4. Deal with Fleshpounds - Unlike Scrakes, Fleshpounds are actually weak against explosive damage, they take 50% extra damage against explosives. Use your RPG or well planted C4s to take down fleshpounds.

5. Know when to use C4 - Unlike Killing Floor 1, there are no pipebombs which automatically detonate against large enemies, this has been replaced with C4s. C4s are remote detonated, but this actually gives you an advantage when they need to be used against large groups of smaller enemies. Buy them at later waves and place them at welded doors, where many zeds would be breaking through. This helps save your RPG ammo as well as deal with a lot of zeds.

6. Buy an off-perk weapon - To help with combat at close range if need be, buy an off perk weapon. An extra 9mm pistol or a katana can do the trick.

7. Don't fire at single or tiny groups of zeds - This will only waste your ammo.

8. Don't bother firing at Bloats - Bloats have massive explosive damage resistance, firing at them will just waste your ammo. A headshot on the Bloat would suffice.

Your 1/2 sticks of dynamite are basically just longer timed HE grenades. But there is a skill you can use when you reach level 5 where your sticks of dynamite explode on impact, this is very helpful as they act as extra M79 grenades.

The HX-25 pistol deals little self-damage and it explodes at any range, don't be afraid to use it at close range. Just make sure to shoot the floor to maximise splash damage, as the impact damage is very low.

This perk's weapons are expensive, you could use the Demolitions perk at later waves where there would be more zeds and you would have more money to spend.

Thanks for reading my guide, I hope it helps!