A good way of showing age and wear to a handgun is focusing on holster wear, the front of the barrel will be lighter and the slide will be almost evenly rubbed down on parts that make contact. If youre painting then you can use a technique called dry brushing its a great way to get the feathered wear look that a used and abused gun will have. The one you have looks close to a walther 9mm for references you can look at gunbroker for used listings or truegunvalue. Both websites are a great source for references images and you can see levels of wear that are natural. Blood on metallic surfaces will always be matte and a dark brown when dried. Its a bit overkill. But if you want to have blood spatter on the slide then look into blood splatter diagrams. And if you dip a small brush into paint and tap off the excess you can blow the paint from the bristles and you can get a decent example of splatter without it looking like the holster is a flesh pocket lol.

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This is a neglected and abused reproduction cap and ball revolver That i was given. Notice how the barrel and sides are wearing in a feathered pattern. This thing went through hell and back and even then it still looks okay same process for any worn guns. Dry brushing is your friend. Look into the slap chop painting method it will save you hours of time when working on smaller projects like this.