If you're still working on it, here's some boss tips. I'll add more as I remember the bosses:
Whispy: try knocking on both trunks parts simultaneously to get whispy down quicker, or if there is only one left and whispy is at least on the touch screen, aim for whispy instead.
Lady ivy: find out when she is going to hit the bar, carry you're kirbys over that half, and when shes dizzy, release. If carrying them over still knocks them dizzy, make sure you at least have 6 or so that aren't dizzy to move the bar down on her head to deal damage. Also, her attack pattern might be mainpulatable, but she always deals the headbutt in a certain pattern, either every third or fourth attack (forgot exact count, but somewhere around that) will be the headbutt.
King dedede: knock both the bomb bubble that's about to explode and the bubble that doesn't explode as quickly into the air, then knock the bubble that didn't explode into the air one more time and it will explode. Its impossible to manipulate him to not use the super jump attack, because the bomb bubbles are the only means of attacking him, and you get to damage him anyways, so its actually better.
Skullord (volcano-pig man): destroy all the meteors and get the cannons right. 'nuff said.
Necrodeus: it is possible to destroy his hands the first time he attacks with each. Just be sure to hit them each time he punches the ground (including when he doesn't get them stuck). For the second phase, get all the damage possible on the two hands as possible before they clap, then escape and dodge the energy balls (you can't destroy them before they clap once). Do it again and they should be destroyed on the second go. Get all your kirbies to one of the hands as quickly as possible and tap like crazy (or, in this case, frame advance-tap-frame advance-no tap-frame advance-tap etc.), and you should be able to destroy the other hand too without it repeating the clap phase, making it so you can instantly go to the next phase (ive accomplished this in real time quite a few times actually). On the third phase, destroy the rocks he throws out not only to stop the lasers, but also to save time (his next action won't happen until the rocks are destroyed). Its impossible to catch him and deal damage when he fakes you out on the touch screen, so you have to wait for when he holds the eye in his mouth out in the open (kirby bosses have weird features sometimes |P). Deal as much damage as possiblebefore he fires his laser, then get off, because you can't finish him in one go. Btw, before this he has a bigger energy ball attack than last time. Im not so sure if it can be negated the first time he uses it via manipulation, but i think on the second time it can be negated. Anyways, now he will fire out skullions (stronger skullys). defeat them like normal skullys, except be careful because they are faster and if you get caught, they don't move slowly enough for you to rescue the kirby. He'll start faking you out again. If he uses the huge energy ball again, find a way to manipulate it away, because he'll most likely use two now. Damaging him more should finish him, then he will shake for a few frames preventing the kirbys from grabbing him, so stay away (it doesnt damage them, but it makes it take a bit longer to do the next step and look unprofessional). As soon as he stops shaking, flick a kirby onto him and all kirbys will follow because it will activate a touch minigame. Touch the kirbys but not the skulls (as if it isnt already obvious). And you won't be able to move while its loading the stage clear screen, but dont end the input there, because you'll need to scroll through the ending, and then theres a fishing minigame during the credits, and then the game album ...
... Since the credits are activated at that point, is it really necessary to play the fishing minigame? Will tas videos just take that part out? Sorry, i dont know how that works :P