Send the PCB to fab house (or print your own if you can handle 2 layers with vias)

While waiting for the PCBs, order all the components (Mouser and Farnell have most of the ICs/passives, while Adafruit and Sparkfun should cover the rest)

Get all the source (schematic, board layout, code, case design) from the Google Drive link on the left side of the project page

Get the code running on your Pro Trinket (you can use a breadboard to try that, but be warned: it will get messy as in the photos I've published)

3D print the enclosure (tip: you may want to merge the bottom part and the sides in a single model, I could not get mine to fit together without using glue)

Play! (hopefully you will when I finish the firmware)