I started latte art years ago, and I can comfortably pour something reasonable in almost any cup shape; however, it was the 6oz (I think) Intelligentsia d'Ancap cup that really honed my skills. The ACF cups are very similar in shape and also work very well.
I still have a hard time pulling off decent art on a macchiato though.
I've tried tipping the cup over slightly when pouring, pouring gently, pouring aggressively, but my espresso and milk end up always mixing together and all I end up with is a pour where a consistently colored mixture rises as I pour, and then I finish with a dollop of the end-pour foam on top.
Like others have said, it sounds like your technique is a little off. You shouldn't be getting the dollop of end-pour foam at all. Either you're stretching too aggressively at the beginning and creating foam that can't be incorporated into the milk, or you're not getting a proper whirlpool/swirl action in the pitcher after stretching.
I would stretch less aggressively but perhaps extend your stretching time. You should get very minimal bubbles, and then work to really incorporate that foam into the milk. Swirling the pitcher after you're done helps for some stubborn small bubbles, but if you stretched too much in the beginning there is little you can do, imo.