Often an actual drip or drop of epoxy won't adhere well due to chalking or dirty decks and the drip will just pop off.

If you have effectively ground it into the surface some with your foot so that it is spread out, sanding it off is about the only way to go. I confess I bought a Dremel Multi tool recently, the Dremel knock off of the Fein, and while even it is not cheap at a hunnerd bucks and you pay an OUTRAGEOUS price for the triangle sander sandpaper for it, it works great for just such jobs as yours.

I suspect that any cheap vibrating triangle sander would be the best tool for the job coupled with a 150 or more sandpaper. Unlike a carbide burr or somesuch it is most forgiving yet the points of the triangle enable minimal contact for spot sanding.

The final alternative in my arsenal of tools is sunlight which in a couple years will yellow the epoxy and cause it to degrade into minimal notice.....I also confess I like the triangle sander idea best.