Once you have completed the model, the normal way to go is to Texture. Some studios will require the modelers to carry this out.

The easiest way to get your bump map correct is to do a UV Layout at the low polystage this gives you the layout of the model in a flat 2D format ready to be added to/edited on Photoshop or other 2D paint package (layer support).

I think the best way to deal with the conversion is to Convert Poly to SubD with the Proxy Object selected or do a proxy smooth. Therefore you can work on the proxy and apply the bump on that instead of the smoothed or converted SubD geometry.

Hope this helps.