Missile Boy has been spanking me for 7 hours straight..
3-2x (Salt + Wound):
This stage is reeeeally bad for The Kid, it's designed to be suited for Meat Boy, so I suggest you practice with him. But it sounds like the problem is near the end where the saws are and Meat Boy makes this easy. If it's the first set of saws, jump down in front of them (where the pile and flow of the salt are), do a full jump to the left wall there, then a full wall jump through them. You'll make it. For the second sets of saws, donít hold run when jumping over.
3-3x (The Red Room):
Trust me on this one when I say that Ogmo is the guy to help you with this stage. His jumps handle very well in this level for jumping through them, more so than The Kid.
3-6x (Not You Again):
You can use Captain Viridian as a guaranteed success for grabbing the first two keys. Then use the conveyor belts to go up the second time. A pretty easy feat for him if you ask me (I used Meat Boy though, lol).
3-8x (Salt Crown):
Itís very easy to get past the first 3 homing missile launchers, so once you get to where the last conveyor belt is (just outside), wall jump off that small bit up onto the platform, but donít stop running. Wall jump once to get up and onto the higher part. Jump over the missile that will be coming at you from the left, but make a very small hesitation about halfway through because of the other missile launcher. Then youíll be home free. You should be in constant motion during this.
Hop over the first pile of salt and then hop up to the left platform. Do NOT wait for the missile, just make your wall jumps up and you should be fine. You need to do a small wall jump on the smaller wall section (left side) near the top before making your jump to disintegrate the blocks.
3-11x (The Salt Man):
I cannot tell you how easy this level could possibly be. The answer to your problems is Ogmo. His first jump is undeniably perfect for going through those saws. Go ahead and test it, youíll succeed 100% of the time once you get a feel. I can tell you that Iíve never messed up even once using him.
I suggest Meat Boy, so this will only apply to Meat Boy. Make four jumps up the left wall (includes jumping off the platform), but hold the fourth one as to avoid the missile. Then make three more jumps up that wall, another missile will have been shot. At this point youíll want to immediately wall jump to the other side, do NOT make another small wall jump before doing this. Once on the other side, make two jumps to avoid the next missile. Hold it, and do another jump before the next missile is shot to avoid death. Let Meat Boy slide down near the saws, then jump to other side, grabbing the key on this jump. Then make your final jumps up to Bandage Girl.
Not much advice to be made here. All I can say is to not hold run and do a small jump forward, thatís how I did it.
With Captain Viridian, wait half a second, and then proceed to fall up. You should be right underneath the platform where Bandage Girl is. Just make your final jumps carefully since you can easily mess up at this point.
3-20x (Sweet Pea):
I assume itís that last homing missile thatís giving you trouble. At that point, stand away from the wall and do a full jump so that it shoots a missile out. Immediately afterwards, run out and onto the first platform, jump to the second to grab the key, then back to the closed off area to resume your safety. Then use the same thing for running out and reaching Bandage Girl.
Hope this helps.