"What?" he reached up with his free hand and pulled a curl down into his face - the yellow vanished entirely and fully went into deep, beet red. So did his cheeks although that was less magical and more just embarrassment. "N-no, I - hold on," because this toothpaste ordeal was becoming awful and he didn't want to swallow it.
And the more Sirius (holy shit) spoke, the more he was convinced this was a wild dream. Time travel?! Okay. He needed to breathe. He held up one finger, the international signal for one second. Then he breathed deep, exhaling slowly. Okay... Think. Right. Of course. Another gesture of one second and a very quick series of spells occurred - one to transfigure the toothbrush into a cup, one to fill the cup with water which he then used to swish and spit back into said cup, and another to clean it all out so he could tuck it into his pocket.
"So you're supposed to be dead. But if I've time traveled. But this is probably a really weird dream so I'm just gonna roll with it," and that was when he threw his arms around Siris and hugged him tight without any other explanation.