The glassmaking skill is required to make any of the green glass, clear glass or crystal glass goods at a glass furnace.
Note that the "collect sand" order at the glass furnace requires the "item hauling" labor, not glassmaking.
Your glassmakers will be limited by the speed at which item haulers can supply them with sand, and by the total amount of bags you have available for this purpose. If you are slowly working toward getting glass production up and running (waiting for a magma glass furnace or for a dwarf with glassmaking skill to immigrate, for example), you may wish to get a head start on sand gathering in the meanwhile. Setting up two or three glass furnaces and a sand bag stockpile for the sole purpose of queueing up multiple "Collect Sand/R" tasks may be an excellent use of your time and hauling labor. With a few dozen sand-filled bags waiting, your glassmaker will have plenty of raw material ready when it is time to begin glass construction. Even while the glassmaking runs the extra furnaces may keep the Collect Sand/R task active to try to keep the sandbag stockpile full while the glassmaker dwarf works.
Note that sand bags count as furniture for stockpile settings but have a special entry that is toggled by pressing u (visible in the lower right of the screen). To make a sandbag stockpile, create a furniture stockpile and forbid the entire 'Type' list, leaving the special Sand Bag entry active. Be sure to disable Sand Bags in your main furniture stockpile, as well.
Glassmaking vs. Masonry
There is considerable overlap between items produced from stone at mason's workshops and items produced from glass at glass furnaces. Masonry is easier to get running and will clear excess stone from your fortress. Glass produces items with higher base value (unless you make your masons use light or dark stone), and using a magma glass furnace essentially makes objects from nothing.