I would think it would be pretty easy to make this.
Unit casts spell...
Casted spell equal to camoflague...
Change vertex transparency to 100%...
Add unit to "camoflagued" unit group...
---
Unit casts spell...
Casted spell equal to camoflague...
Unit is in "camoflagued" group...
Change vertex transparency to 0%...
Remove unit from "camoflagued" unit group...
Yeah, should be pretty easy.
But, hell, I can't make much better
Edit: I checked it out. Its a very nice spell. Does something different than what I thought it would. I still can't make much better.