My current workflow is to model in MOI, obviously :), making sure to keep separate copies of parts / models pre boolean so that I can easily alter things / reuse items.
Each part of the model I will want to be a different material, painted steel, chrome etc. I assign to a different style.

Once finished I export a low and high poly version of the model in obj format as triangles, tweaking the low poly setting to see how little geometry I can get away with and still retain shapes.
I then take the low poly into 3D coat (https://3dcoat.com/home/) and use the auto UV options to quickly generate a good enough UV in a couple of minutes maximum.
I then apply the UV's out to the model with only one material applied, this is because I only want one UV space for the whole game model.

Its then over to Substance Painter (https://www.allegorithmic.com/products/substance-painter), I import the UV'd low poly model and then bake ID, normal and Curvature maps from the high poly model.
I can now easily apply different materials to specific areas by masking using the ID mask and generate wear effects automatically using curvature maps. The normal map from the high poly model gives me nice smooth rounding on curved surfaces. Once done I simply export out the game ready maps and apply.

Taken together I can therefore go from finished geometry to textured game asset extremely quickly with minimal effort!