Cool tutorial, Cybermonk.   mmm... doughnut...

I always wanted to try something like this.  Plus, you've given me some ideas for future projects where I can employ this technique, and change the instances to real items.  I usually go with the multi-duplicate meshes way.  This will be much more efficient.

What was the hiccup in the icing selection?

Was it because you decided to turn down the weights to zero, and then paint in only a line of weight-mapping?

Did this hinder going back to 100% full weights on the vertex group, and did you undo your weight painting first?

Nonetheless, thank you for the tutorial.