Okay, so my findings. Someone come in and tell me something I'm missing.
First, grease. There's just...no point. Not unless you want to do a self-mutilation dark-steel setup, which will take too long and will get you hurt a lot in order to create enough grease. I suppose arguably fire-steel could be interesting, in that you could use Grease Throw to fill your foe's hand full of grease, then torch him with fire. This would probably do well as a primary fire type, so that your attack did big damage, but still. Feels underwhelming. I'm sure Piston Shot and Grease Cannon do some insane damage if you can ever get a lot of grease, but I just don't see that happening too easily.
Railway, on the other hand...well, it takes forever and a day to get a steel level high enough, but it's devastating. Problem? Get hit with a ground move while you wait, even a weak one, and it can mean serious problems. I actually had three Railway Construction cards in my hand at once, and started using them. Ended up with something like twenty-two railway cards in my hand, which would've meant pretty much instant death for Train Tackle and likely insane damage from Train Whistle, but I'm not sure it's worth it.
Mirror deck, on the other hand...this one is interesting. The idea here is to grab every single mirror card in the game (seriously, I'm not kidding here), then slap in Link to the Past (trust me, you'll see in a minute), a couple of healing cards (because why not?), Fairy Aura (if you can spare it), maybe Screech, and a bunch of special steel attacks (the lasers, plasma thrower, etc). You don't absolutely have to stick to special, if you'd prefer physical. Anyway, here's the idea. You're almost sure to end up with several mirror cards in your hand that won't trigger. That's okay, leave them there. Build your steel level up a bit, junk a couple of cards, and once you're strong enough, the strat is simple. Mirror Throw will toss all your mirror cards away. Mirror Repair will give them straight back to you. If you have multiple Mirror Throws you're in business. Alternatively, keep a Mirror Ray or two around for when your hand is big and full of mirror cards. It takes awhile to get going but it's kind of hard to stop. Link to the Past is a potentially good way, when your hand is thus full of mirrors, to get back all the cards you burnt. Fairy Aura, if you're lucky enough to have used it, will protect you from the chance of curse. And even if it doesn't, curse isn't too devastating. basically this deck will ensure that you can use cards over and over again in a cycle, provided you live long enough. There might be a more optimal way to do it.
Check out my Manamon text walkthrough at the following link:
https://www.dropbox.com/s/z8ls3rc3f4mkb … n.txt?dl=1