I just finished a small series of the PissOff project. After all work done, I probably would use a stencil and solder paste next time.
For this series I used a slightly larger speaker to improve the loudness and sound quality. Tried some different ones, but the really good ones do not fit on the back of the project anymore.
While soldering all these boards, I found out the contacts of the SD card holder do not always easily connect to the PCB. If the SD card is not working, resoldering these solved problems for two boards. Also in one case, flux came into the trimmer, there was no contact anymore and no sound output.
Read everything about the project here.