Your first step is to make accurate 3D models. You could have your local draughtsmen make these for you, but you'd be better working with Dershr Engineering. Here's why:

A recent Dershr Project

We were asked to re-design a part for a major multi-national [you know them very well, and you admire their products].

Our re-designed parts are:

lighter [less material = cheaper]
stronger
no shrinkage/deformations
look better
fit together properly
removed ugly flow-melt lines within the plastic
our re-design ease assembly of the product, adding efficiency to our client's process
lengthen the life of the tooling
re-design time was much faster than their own in-house engineers

That's very impressive for just one case, and also for such a prestigious client.

If we can help such large companies so well, we can help you too.