This is a guide for every (MP) Story mode achievement up to the Hydrator.
First, you should know how to play this game, so I'd recommend beating the game in single player, almost every level is exactly the same in multiplayer, so if you can beat it there, you can beat it here.
Next get two controllers (xbox 360), learn how to use the keyboard (not recommended, but up to you), or get a steam controller and learn how to remap the keys. If you get a steam controller you can put both players on different control pads. (And even make a 4 player controller set up, I did!)
Then you should play the multiplayer mode. Now there's two things to know here. First, don't aim for golds, you're trying to beat levels, not get golds, gold will likely take two players working together, and would be very hard if not impossible for a single player trying to play two player mode.
Second you have skips, use them liberally. Once you run out of them, go back and clear the levels you skipped. There might be a few levels you can't do with two controllers, skip those. But you can beat enough levels up to the end of Hydrator with just two controllers and skips that you don't actually need a second person with good use of skips.
This will take some skill, and on levels where there is the blue barrier, you'll need to switch players to work on both sides of the barrier, (or die and get teleported across the barrier) but this is VERY doable, if a bit frustrating.