That last piece of advice has been repeated over and over again during the last months. Anyone who uses fan-created Ages, ULM, flymode, my own City imports or anything that modifies Uru, without first taking a backup of a clean install is asking for trouble.
For Drizzle, the process is actually very simple:
1- Take a backup of your current Uru files
2- Use Drizzle and convert your MOUL Ages
3- Play around your MOUL AGes
4- When finished, copy the changed files from your backup.
Also, what you're experiencing, Andy, has been described before. That "special effect" is not particular to MOUL converted Ages. I recall someone had great fun with mixing Ages as early as 3 years ago. An explanation was posted here recently, I just can't find it again.