step 1: block out your basic colors, making sure none are absolute black (white is fine)
step 2: wash using a dark shade that wont ruin the base colour, dont bother making it heavy, it just needs to be dark enough to see the lines.
step 3: do your absolute highest highlight now, dont bother getting it thin right now, that part comes later (and if you do, you'll probably have to repeat this step after step 4.
step 4: take a fine or super fine point brush and using your black paint blackline every transition of material, colour, and any sharp recesses.
repeat steps 3 and 4 till you have nice even black lines.
step 5: take an intermediate colour and go over half your highlight lines,this thins the highlight and blends it with the basecoat.
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will be adding wip pictures soon