How do you paint a sign using two different colours?

[Shane]

How do you paint a sign with engraved areas and keep it looking professional without the colours blending together? I have attached an example of sign that I'll assume is painted in two different colours.

I've tried hand painting the engraved areas but the end result is not a crisp clean edge between the colours. I've tried spraying the engraved areas and then rolling another colour over the top but this causes the roller to dip slightly into unwanted areas and also a rolled finish doesn't look anywhere near as nice as using a spray gun.

I'll be working mainly with MDF and hardwood timber. Any help would be great.

Shane.