Because I currently don’t know of any existing GIH-Blood-Brush, you would have to create such brushes yourself.
Our forum member @fizzyflower offers a brush pack containing at least five blood brushes. If you want to support her work and drop her a tip, you can buy them via GumRoad, but if you want them for free then use the Google Drive link instead:
If you are in need of source materials like pictures with (blood) splats, you can search through any of the websites offering free resources, like CSP & PS brushes (from which you can extract the contained brush tip pictures (if I’m not mistaken you can unpack Procreate brushes too)), or brushes for other programs if you know how to extract them, furthermore you can scrape picture hosting sites, etc., it was never easier to find resources like nowadays where lots of resource offering websites try to attract new users.
But there is one source with an enormous amount of diverse resources which is worth the registration needed to download something from them, and that is DeviantArt. It is similar to YouTube with DA, I don’t like that site and their politics and rules and how they treat their users, but their content is at least worth a registration, you don’t have to give them your main email address, you can use one from the many free email services and feed them with fake data.
So, now a few more possible ideas for you:
Here you find a YouTube video on the (blood-)spot for creating such brushes:
https://www.youtube.com/watch?v=HW2Mp18-g7c
Here are a few possible candidates from DA, in case you need support in unpacking PS ABRs (Adobe Brush Resource Archive), I can help:
https://www.deviantart.com/project-gimpbc/art/Blood-Brushes-by-KeRen-R-32864474
https://www.deviantart.com/sanderndreca/art/blood-brush-high-quality-126106932
https://www.deviantart.com/project-gimpbc/art/Shadow-GFX-Blood-37468400
https://www.deviantart.com/anulubi/art/BLOOD-STOCKS-813099826
https://www.deviantart.com/scully7491/art/Blood-5788524
https://www.deviantart.com/annfrost-stock/art/Blood-splatter-brush-105318215
https://www.deviantart.com/redheadstock/art/Blood-Spots-Photoshop-and-GIMP-Brushes-12388500
https://www.deviantart.com/redheadstock/art/Splats-and-Splatters-Photoshop-and-GIMP-Brushes-71906199
https://www.deviantart.com/redheadstock/art/Dripping-Photoshop-and-GIMP-Brushes-66402927
Michelist