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It is definitely possible but it's so complicated (for little reward) that I never bothered. XD was hard enough for me :P

But to answer your question yes you use the XD RNG, and yes flawless spreads are possible :)

I think a flawless careful one is no little reward. Since Body Slam is a very good move on Jirachi! Yeah XD RNG seems a lot of pain but it's definitely worth it for some Pokemon