This was for Technique Challenge #94 a couple of weeks ago on Stampin' Addicts.
For marker thumping just choose a solid image stamp (not line art).
1. Ink your solid image stamp in one color.
2. Use a marker to add another color (or two) to the stamp by thumping the marker sideways onto the inked stamp. Be sure not to pounce the tip of your marker onto the stamp...it will damage your marker irreparably. Perhaps if you have an old worn out marker the angle of your addition of the marker ink wouldn't matter.
3. Huff to rewet/moisten the ink on the stamp.
4. Stamp your image.
5. Finish your card.
You also might want to gently scribble any extraneous colors from your marker onto scratch paper before putting the marker away.
The bluer butterfly in the middle of the circle of butterflies was stamped in Marina Mist with Wisteria Wonder thumped on it. The other butterflies were all stamped in Wisteria Wonder with Marina Mist marker thumped on it.