3D printing is the greatest gift for Makers. However, if you are serious about developing your own hardware, invest in an SLA 3D printer or send your prints to a lab with SLA equipment. It is especially true when the design has a lot of fine details.

SLA printed parts has very fine surface. Most of the time, I can just spray paint it directly. Also, SLA has much tighter tolerance than ordinary FDM printer. When printed parts needed to tight fit together, SLA will save you a lot of time to get rid of that extra 0.3mm layer of plastic. 

It is very important for the SonarPen prototypes to have minimal manual adjustment because the adjustment is hard to repeat. When the team members have prototypes that are different and behave differently, the works produced are useless. Thanks to SLA technology, my team didn't have such issue.  

Spray painted SLA printed part(above) vs FDM printed one(below)