How do you do this? Just use those rooting powders? I would do this mint even though I have some seeds that already sprouted.
Well, herbs like that (especially mint) are notoriously easy to root and mint especially will form runners which root at different points along the ground.
The best rooting hormone is not powder, but a liquid hormone (a cocktail of several hormones actually) called Dip 'n' Grow. Professional horticulturalists use it for nursery/greenhouse propagation for several reasons over powders:
-it absorbs into the plant better, being liquid, and also absorbs more evenly
-it contains more types of hormones than powders, which usually have only one
-it can be diluted to different strengths for different cutting types (woody, semi-woody, softwood, etc.)
-the solvent for the hormones is alcohol (powder hormones are talcum powder, which is very fine and dusty but still doesn't absorb as well and can't be sucked up by the vascular tissues, and also powders aren't soluble in water and float, leaving a nasty white muck), which sterilizes the dipped end of the cuttings and prevents mold/rot/fungus/etc.
You can use powders and they'll work fine, but I get better and quicker strikes with the liquid.
Also as with all cuttings it's quicker to maturity than seed as well as true to type. And keep humid, moist, enclosed in a bag in a place without direct bright light, just like any other cuttings. Sterile and airy medium (basically peat/perlite/sand).