My then-girlfriend's brother once did an Airfix 1/72 soldier as a casualty. The man was throwing a grenade (I think he was British WW2 infantry), so he was stretched out. My friend took off the stand, so that the man would lie on his back. Then, plenty of red paint for blood and little strings of off-white modelling clay for the guts and voila! A very dead guy.
I don't bloody my troops up, but then they're mostly using plasma, fusion, and laser weapons and wearing sealed armor, which will contain the bodily fluids that the energy weapons don't completely boil off.
Hand-held plasma and fusion weapons and vehicle-mounted lasers will probably boil all of the water and other fluids in your body instantly, so while there may be some pink mist in the air (best simulated with polyester batting into which pink paint has been worked with your fingers), there won't be much blood.
Hand-held lasers will probably boil off a couple of liters of bodily fluids instantly and cauterize the wound, so again, not much blood.
Gauss rifle rounds are very small (2mm or 4mm) and very fast, so they'll probably tumble around inside your body with a lot of energy, tearing up all of your internal organs, but not causing much external bleeding.
