So here are the bloody hands I did for last years Halloween Party. It turned out really good.
I used red water based paint. Squirted out paint on my hand rubbed them together then just placed my hands on the surface (not even) then dragged my hands down. As I got to the bottom I picked up my hands so the red paint got faint. The shower curtain was clear and I added a small battery operated tea light candle to the window. It totally looked real and the kids loved it. After Halloween clean up was a cinch with window cleaner.
Conclusion: Kids loved this so it was a success.