In my previous posts I was modifying a traditional plastic-housed USB Keyboard that had a chip inside it like the one below:
These contact points had to be scraped or sanded clean in order to solder to them, however scraping them made them quite thin on the surface and therefor quite brittle.
The chips inside the cheap, flexible silicone keyboards (above) are actually much easier to work with because they have a line of female headers instead of contact strips. This allowed me to solder up a vero board to act as a breakout shield (below)
I bought some female-female jumper cables which I will be cutting, stripping and placing a n/o button between. This allows me to plug and play the buttons as needed with low-risk. The layout of the header pins on the vero board was determined through shorting sections of the chip with test leads and figuring out the combinations necessary to make a minimum of 25 unique combinations/keystrokes.