He is a complete guide to the demolition perk tree. If only so there is one. One essential thing is not feeling shame in restarting from a checkpoint. Don't worry, I will tell you when you will need to. Plus, it is tracked even with the restarts so don't worry.

Second, these do need to be done in an order. But I'm pretty sure you know that already.

And Third, the random German is part of a joke and not to be taken seriously.

Without further ado...

Kill 2 enemies with one grenade

Easy enough, find a crowd of soft targets. Truth be told, took me awhile. But this isn't the hardest one...

Kill 10 enemies with grenades

Easy enough, it adds up. Just find a good place to throw one into and you'll be fine.

Kill a commander with a grenade

...You might be asking why I made this guide...

That aside, if you got stealth down, just toss one to a commander standing idle. He won't get away in time.

Kill 5 mechanical enemies with a grenade

And here we are, the hard ones.

The big robots are a bit too hard for this, as you will likely kill it by accident. Instead, seek the little flying ones. First, get them close to ground. Good news, their movement isn't too good.
They start and stop slowly, so picking a moment makes the difference.

You can get it easy in the moon dome at London Nautica. With the added bonus of luring drones into the moontop control room to blow them up. The small room will all but guarantee the kill.

If all else fails, reload the last checkpoint.

Obtain 5 kills within 10 seconds using dual-wielded rocket launchers

First, you will need the rocket launcher upgrade on the bridge level. From there, go to the u-boat level. In the room with the two shotgunners, kill them quick.

Then, go around the side and take the unarmored naval soldiers out. Remember, you need to duel-wield. If it doesn't go according to plan, restart to the last checkpoint.

Obtain 5 indirect kills by dropped enemy grenades

I recommend the first level. The flesh is softer, and drop easy. At the flack cannons, stay in cover until you hear the shout. Shoot the soldier with the grenade out. Despite less armor in 1946, they might even survive the drop. They won't survive the explosion however...

And again, if need be, restart to the last checkpoint.

Obtain 5 kills from thrown back grenades

This is why I made the guide in the first place. More people have finished this game on UBER than gotten Sentinel. Which makes it all silly on how easy it was when I got a strategy for it.

Back in the U-boat level, past the first area, you will get to an area with six cabins. Kill the guy outside of the cabin area and take cover until they throw a grenade. The U-boat has narrow halls, so it shouldn't be too hard to throw back the grenades. With Bullseye it gets easier with the explosion on impact. You might need to restart from last checkpoint, but it will add up. You will have it in a few tries.

Obtain 50 kills with grenades or rockets

Just like Grenade pouch, it adds up. Keep trying and you'll get it. Don't worry, the hard part is over by now.

This should help get all the demolitions perks. If this guide blows up, maybe I'll make one from the duel-wield tree.