You can get it. You get a female Dragonite with the ability Multiscale, then breed it with a male Dragonite with the move Extremespeed. Since it's an egg move, the resulting egg will gain Extremespeed, with a chance of getting Multiscale. The extremespeed Dragonite as you probably know, comes from the Dratini you get in Heart Gold/Soul Silver.
Normally, you would be unable to get these abilities through usual breeding. However, if the female Pokémon has the Dream World ability, there is a high chance that the ability of the offspring will be the ability it has listed for Dream World abilities. However, if the male Pokémon has the Dream World ability and the female doesn't, and if you breed the female with a Ditto, the Pokémon will definitely not get the Dream World ability. -Serebii
Extremespeed-You asked for it. (See above on how to learn)
Fire Punch-You asked for it. (You'd have to use move relearner)
Dragon claw-STAB (TM)
roost-Restores his health.(TM)
Personally, I'd put something like Earthquake,Stone Edge, Super power, Aqua Jet, ice punch, or Dragon dance instead of fire punch on him, but that's just me. You could also try out light screen to better take attacks if you wanted.