A good moveset for Arcanine was going to be this:
-Sunny Day
-Flamethrower/Fire Blast
-ExtremeSpeed
-Iron Tail/Hidden Power Water/Grass/Electric
How to use? Start the match launhing Sunny Day and after keep attacking Flamethrower/Fire Blast. If a foe reistante to fire (water, dragon, fire) were switched out, then use ExtremeSpeed and if it is rock type, use Iron Tail. If the IV's of your Arcanine were electric, grass or water type, it should be better put it over Iron Tail (or Sunny Day) once that any of these types will cover most of Arcanine disadvantages.