Alien Swarm: how should we go about Oustanding Execution?

I've got most Alien Swarm achievements under my belt. In fact I'm missing:

1. SynTek residential speed run (time limit on a map)
2. Nuke from orbit (kill 100,000 swarm)
3. Outstanding execution (complete the entire campaign without anyone dying)

Nuke from orbit is basically easy (dunno if I'll even try though), and I'm sure the speed run can be done with some practice. I'm sure Outstanding execution would eventually come by just grinding, but seriously, that's a lot of work. But it's the achievement that I want most (after Hardcore, which I already got).

I think the main problem is stupid deaths. The friends that I'm playing with can handle themselves, same as I. We usually play hardcore friendly fire so we've learned not to kill each other (except the occasional panic), and we rarely play below hard onslaught at all. So the basic potential should exist, but I just don't think we'll manage a full campaign even on normal difficulty by playing the usual way. Yes, we've briefly tried on a couple of occasions.

What advice would you give?

I'll duplicate some stuff from Dalshim, but some of his points are not so important, and some are missing.

• Play on Normal
• Stick together
• It's better to have a non-full team (i.e. less than 4) than to take bad players into it. Three players is OK.
• If you want to take Hornet Barrage (or, even worse, Smart Bomb), better take Electric Charged Armor (it's very useful, not only against parasites which may ruin your session) or Freeze Grenades
• The more medics the better (the best loadout for medic would be Flamethrower + Healgun).
  You shouldn't be a peace medic; such characters are just too vulnerable!
• Use Jaeger with Vindicator to kill the aliens efficiently! It's a complete disgrace to take Flamethrower if you are an officer.
• Tech could take a sentry (a simple one, not the "sophisticated" but less useful ones) for the missions where you stay in some place for a long time, and Officers can carry Incendiary Mines which are even better.
• In my personal opinion, Special Weapons class is mostly useless. Better take one more medic.

Here would be my advice :

• Play as a team (you already do)
• Play in normal mode to make it easier (you've already figured that out)
• Have a full medic (with both gun and medic packs to put on the ground) or at least with medic gun and play around him he is the center of the team.
• Take items that stun / freeze / slow but don't do damage to help a teammate in bad position without destroying him (best example : Freeze grenades).
• Secure some positions halfway if someone is low health to take time and heal everyone with health beacon (use turrets if needed to secure position).
• In normal, its really easy, so use a fighter to open the way and another one to close it, put medic and engineer in the middle.
• Don't separate to finish faster, its the best way to make stupid mistakes.
• Rush is better because aliens don't have time to spawn, but only if everyone is following and you protect medic well.
• Don't fight all with flamethrower (because it doesn't kill instantly), one or two is enough.
• Don't use grenade launcher, it's the best way to make a stupid mistake and kill a teammate (use freeze grenade instead)

That's about all, it's usually fairly easy to achieve if everyone stays concentrated and doesn't run around alone thinking its too easy.

EDIT : For synteck residential speedrun, can't remember the names but if its the first one. All members of the team need to take chainsaw to destroy doors, it goes faster than using adrenaline with an engineer or unsealing. Also use weapons that don't slow you when using them or recharging (shotgun is good, flamethrower isn't).