From the beginning, I started by a block out AK. Easy and simple.
After I was satisfied block out AK, I built detail parts, one by one. I kept it at low poly version, but still ensure I had enough edges for Curve.
For wooden parts, I will sculpt in Zbrush. For metal parts, I still keep low poly and make another version with Bevel Edge for Normal baking. You can see it at below tips.
Tips: Why didn't I make a Hi poly for metal parts ??? Because I only need Soft edge shading on each Hard Edge. With this method, Low version will fit 98% Bevel version ( I only bevel hard edge). I think we will have a good normal map.
Here is result of this method. You can see. Hard edges have a good shading, right ??
Tips: Sometime, I got a bad shading ( gradient shading) on Bevel version after beveled hard edge on Low version ). This bad can cause a gradient on Normal map ( Bevel version will be High poly when bake). So I remove these edge to get flat shading.