With the same Ochre Brown and Sunny Skintone, I edge highlighted the leather straps trying to not be very precise. Some tremble in the brushtrokes is desired in order to get a worn look.
For the scratches and cuts, just draw the scrach with the same mix, and if you want to simulate a deeper one, place a very thin line of very dark brown or black on the interior.
Add little dots of Scale 75 Heavy Metal for the rivets.
Vallejo – Sunny Skin Tone