Here's one of my weird craft projects. This spirea bush bloomed a month or so ago--with a few new blooms still popping out from time to time. The dead flower heads stay on the plant. So I sprayed a lot of them pink. Then I followed with a light burgundy spray.
Voila! A bush that looks like it's blooming. I plan to tackle the astilbe next.
If you want try this technique in your own garden--make a cone of newspaper and grasp each bloom before you spray it. Do the pink layer first. Then when it's dry--in a half hour--do the burgundy layer. It would also work with a butterfly bush. Or anything else that leaves feathery brown flower heads.