For the blood spatter I wouldn't use an airbrush. Take an old brush and put some paint on it. Pull the hairs back and release towards the mask and you'll get a verry realistic spatter effect (used in my last piece). When testing this I found that it looks better if you use burnt umber first and a real bright red next.
I've never done a mud effect on an item so I'd test whats comming first (this is just how I'd try it 1st if I had to do it and I also would first do it on a test also )
With a texture mask and burnt umber I'd first map out the area's I wanted the mud in (texture FX mask from arttool or something home made resembling it). Next soften up the effect from the mask by "scribling" over it with the burnt umber.
You should have a nice muddy texture now that will indicate the next few phases.
You'll now will want to create the illusion of depth by adding shadows and highlights. As this is a 3d object the safest way to do this is pretend the light comes from above and in the front (will mess the least with the real light it catches)
With a lighter brown (or burnt umber with some white and yellow) just pick out the parts of the texture you created that would look good with a highlight and scrible the hiughlights in (you stay away from the parts of the texture that are dark but only pick out the lighter parts for the highlights)
With an even lighter brown pick out the realy light parts of the highlights you did before to give them a bit of an accent.
Add some black to the burnt umber and accent the darker area's where needed maybe use it roughly to add some general shadow in the area's where you have a transition to the background color.
Throw some actual mud at it??? (thats me saying I have no clue ... maybe have a look at a model forumI think they have more experience with actual 3d textures)
first attempt at making the panels. The bottom one is bad but the top one I don't think is too bad. The black dots are just reference points not final rivets. What you think
I use masking tape for the panel edges, just mask on the side your light source is coming from and let the overspary work for you.
Here is a bike I did with the paneled look:
@bpwmd I dunno what time zone you are in?
I will do a step by step for you today and and post it later ok. Once you have seen it you will see how simple it is