Not really guaranteed. You have to craft the right comment and have him read it in the right timing and the right atmosphere/mood to really produce gold dust with a paid comment. In a way it's like playing the DSP gacha. Sometimes you get unlucky (he just LIMBs the superchat, says "I got a troll tip haha what a moron"), sometimes you get a decent pull, sometimes you get the ultra-rare gold dust.
Which means just like actual mobile game gacha you shouldn't do it. Leave that to the whales who can afford to play it like the detractors who mahnetize Phil.