I'm not gonna invite you to a lobby as it's much easier to just do it by yourself since you'll get more points that way. so if you want to know how just read below

I'm assuming that you're on about the Act 3 Chapter 1 boost which is the level with Hoffman.

If so there are two different methods, the first is the one I feel more people to more often.

Method 1
Start Act 3 Chapter 1 up on insane with the mutators; Super reload; No ammo pickups and enemy regeneration, this way you can have super bullets with the smallest of xp negatives (95%).
Stock up on ammo, and go up the right hand stairs.
(Optional: From the top of the stairs there will be multiple reavers flying over, these are umlimited and you can kills these until you get a 10X bones)
Now just carry on to the front and kill the locust until the catapult appears.
Now go back the way you came on to the platform to the right this will give you a great view of the enemies as they come through the gate.
Continue killing them until the maulers show up.
At this point you can kill the first two sets for extra points but remember to let ATLEAST one to the gate so they get through, now fall back to the first area.
Continue killing these until the boomers show up.
Kill some of the boomers and allow one to get through while you fall back to the main room, stock up on ammo and set up behind the sand bags.
Now just finish em all off. on average you could get around 800,000 - 1,000,000 points.

This second method is what I prefer but it takes alot longer.

Method 2
set up Act 3 Chapter 1 on insane with the follow mutators; Super Reload, No ammo pick-ups and either friendly fire OR enemy regeneration.
Swap the gnasher for the Sniper and set up at the top of the right stairs you will see reavers constantly flying over kill these with an active reload sniper, it takes one shot.
Keep killing these until you get your desired points, people normally go up to around 3.5 million.
From that just finish the level without dying and you should get alot more points than the first method but it will take alot longer.

Hopefully this helps but if not I've left some videos below.
Method 1


Method 2