I just assumed a bit of water in advance would prevent toothpaste from directly/easily adhering to the bristles, keeping more of it "in useful circulation" as it were.
> kinda gross
A few months back I needed some hydrogen peroxide, but the available bottle was more than I was likely to use before it degraded into H20... So, naturally, I started messing around looking for other applications. (It worked great on certain oily gunks that resist isopropyl.)
One weird outcome from that is I've been putting a drop on the bristles of my toothbrush, although it's more of an idle experiment to see if the foaming action dislodges visible crud (i.e. toothpaste near the base) in-between uses, as opposed to a disinfection right before use.
And, yes, definitely water first. It's sitting out there exposed, rinse it off!
One of the niche magic ingredients to look for is TSP. Alongside bleach (consult proper sources for actual ratios) the combination becomes more powerful against mildews.