First Aid special effects (skin and blood) always made it fun to learn first aid.
Mortician's wax to hold on any funky attachments. Mortician's wax can be purchased at any costuming store. It was also useful as the "starting point" for bleeding wounds such as bullet wounds, impaled objects, and lacerations, in addition to open fractures.
Turkey and chicken bones for extruding bones, Plexiglas for flying glass.
Blue eye shadow strategically placed for simulating shock.
Burnt marshmallows exteriors for burnt skin.
Vaseline with white tissues over them simulate blisters.
Ground rouge and then ground charcoal over the top of Vaseline for third degree burns, tissue (either Kleenex or toilet tissue) over the Vaseline and rouge, then possibly torn and lifted up for the blister) for second degree burns; this can also be added for third degree burns, just don't use the charcoal on second degree.
For blood use blue liquid laundry starch with red food coloring added. It sticks well, it gives the coloration of blood, and dries with the consistency of real blood. Or a mixture of cocoa and water with food coloring, placed in squeeze bottles drips marvelously. Very gory.
For a simpler simulation of blood: mix catsup and face cream.