well, you wouldnt want to use those types always, because you might kill it...
here is my advice
1.save the game before trying on ho-oh (just before you click on it)
2.put it to sleep with a pokemon thats faster than ho-oh...
3.change to any pokemon and use flash until you cant anymore...
4.weeken it until it is low in health (use a strong move then weeker ones and weeker ones until the thing is red)
5.whenever it wakes up, repeat step 2
6.whenever it uses recover (which it will) repeat step 4
7.throw ultra/heavyballs whenever it is asleep and in red health
8.if you accidentally kill it, purposefully kill it, or run out of pokeballs, then turn the game off, and repeat steps 2-7 again...
p.s.whatever you do, do not burn, poison, or confuse it, because it may kill itself...
dont paralyse it, because then you wont be able to put it to sleep
freezing it is good though...
and dont give up, it may take some time to get it, but you will get it eventually...
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and this one...http://gameknot.com/?rfr=diezombie...when you sign up the second one, where it says referals by, type in diezombie