I'm pretty sure Ammy's brush techniques are more or less instantaneous, for all intents and purposes. The only times it's been outdone is if there was someone else with the power of the Celestial Brush (ie, Ninetails or Shiranui).
Not that it matters, Amaterasu is about a fraction of the God that Arceus is made out and shown to be. The only clemency for Amaterasu that I can think of here is if we're regarding her when at full power (aka, Okami 'Shiranui' Amaterasu). In that form, all the brush techniques are apparently a few folds stronger, and s/he's shown to be able to resist time powers (or at least break out of them).
[SPOILER - highlight to read]: In Platinum, the only way to get Arceus is to have the Azure Flute which is the final event item from Nintendo WiFi. HOWEVER. It was never released! Theres no other way to extend the stairs so The Scenario was right all along and I was lying! And you fools believed me! Zehahahameowhaha!
Not if the first thing she does is to draw and create said ball.
Yeah, then Arceus wins if he has to be weakened in order to be captured.
That said, isn't the Arceus that appears in D&P weaker than he was when he created everything?
Her brush techs take no time at all, and are instantaneous. Time is frozen when she uses her Celestial Brush, and the effects occur immediately. So no, it would not take any time at all compared to their moves.
"To all visitors from Transylvania looking for the head of Voivode Dracula: Yes, we have it. Yes, he's dead. No, you cannot see it. No, he will not return and invade you again. It has been over thirty years, please stop pestering us."
^Yes, because even God characters have tiers, and Ammy is leagues below the likes of Arceus, especially since the entire universe and the creatures who would uphold the natural laws of said universe count alot more for many things. The worst thing Yami was ever known to do was sick a group of monsters on a bunch of virtually defenseless angel-esque beings during an escape attempt.
Then there's the fact that the term "King of Darkness" or any such synonymous term is among the most applicable aliases. Honestly, if titles mattered over showings, Monster Hunters and the monsters themselves would be on the same level as something like Warcraft top-tiers, where in actuality, not an army of Hunters would hold up against Deathwing.