Glad you enjoyed the post! To answer your question — without seeing your set up, mind you — the best I can suggest is to use a category tag that has easy to remember modifiers for groups of children. Something like Project-Name, -PN-Subtype1, -PN-Subtype2, etc.
A better option may be to first explore the Springpad tagging system and how it works within the structure of Springpad, itself. Experiment a bit and then create a whole new tagging system that will best represent your new workflow.
Hope that’s helpful!