A few horse questions?

I don't use martingales so I can't help you there but I would say you half chaps are to big, ther shouldn't reach your knee, they should sit just below where your calf starts to slope up to your knee. And the only way to get dirt and stuff out without washing is to curry comb it, but once your don't that I would spray some line show shean or something similar, it will prepell diry and help to keep it from getting cake into his fur