The reddish tube is for use with Bondo, the clear tube is used for fiberglass resin, so you only want to buy the red. Basically you get a large can of Gray puddy, kinda like a soupy clay. You mix in a very small amount of the red hardener and produce a pinkish puddy. the more hardener you mix, the faster it cures. There is usually a small spatula that's included with the kit which is the approxamate color you want for a decient working time. As far as working with your fingers, it can stick to your skin, but you usually apply it with a plastic spatula anyhow 
I would wear a dust mask when you sand it, it can come off pretty fast, so you want to sand lightly ..... unless you really load the stuff on 
As far as an adhesive, it bonds to the surface of what you're applying it to, but can crack and seperate if the parts aren't connected properly, so you basically want to use Bondo for filling cracks, building up surfaces, and evening them out and not for attaching them..... at least that's my experience with it. You can get a quart can that includes hardener at auto parts stores and larger hardware stores.... but you usually need to buy more hardener, which you can buy seperately
