Oh I think the technique you are talking about is the copy paste and flip for objects that are in front view to avoid redundancy hehe. If so, I do it sometimes too. I wish we can do it always to save time lol.

Congrats on achieving the look you want. Highlights are always needed. A little gloss will always complete the look of any drawing. The thor style helmet suits her too. It doesn't look girly and it gives a balance in the drawing.