Attached Link: http://www.poserfashion.net/tablecloth.htm

Probably the "tablecloth" tutorial at Poserfashion.net is what you want. Only instead of the tablecloth and table, use the high-res square and the horse. Position the square above the horse, and go from there.

You don't necessarily want the shortest possible animation. You want to give the cloth time to drape fully. Then you can pick the frame where it looks best, and export that.