You are correct about corn syrup based bloods. They never dry. At best, after a few days in the air they just become thicker and gummier; not what you want.
I make my own gel-blood by mixing knox unflavored gelatine, glycerine, and sorbitol (the later two you just ask your local pharmacist for. The sorbitol might take one business day to arrive, but they're pretty quick). Stir up equal parts by volume and put it aside for like 8 hours or so. microwave it for 30 seconds at a time, stiring it inbetween (or use a double-boiler).
once everything is well dissolved (shouldn't be grainy at all) mix in red food dye. for larger batches, I do something like 40 drops of red and 1 drop of blue. You'll probably need less than that.
once the food color is mixed, take it off heat and let it cool. Either seal it up tight and use it later, or wait until it is cool enough to have comfortably on your skin, but still warm enough to be spreadable. Be careful hear. If you put it on your skin while it's too hot (and remember, there's a major jelly-donought effect going on , so the center of the bloob quickly becomes the hottest part) the stuff is like napalm. Keep a washcloth dunked in a large bowl of cool water at the ready especially when getting used to the stuff.
If you screw up the application, you can just put it back in the container and heat it again. As long as you don't bring the stuff to a boil or get it dirty, it can be recycled over and over again.
If it cools to a tacky surface, you can apply a little face-powder (or talcum powder or corn starch); but use it sparingly and rub off as much as you can with a soft brush. It makes the surface less dull, which is bad for the appearance of fresh blood.
Sometimes when I'm lazy, I instead mix up quick batches of Platsil gel-10 silicone and a bit of red pigment. It cures automagically 10-15 minutes after mixed (shorter if you add accelerator) Sometimes I add some plat-thix or tin-thix if it's too drippy during application. But this is mostly because I always keep lots of the stuff on hand. It's probably not worth buying all that stuff just to do random fake blood effects.