I won't even fool with dry fertilizer while planting, even for my garden. Just too much trouble cleaning out hoppers and such when liquid is SO MUCH easier, ESPECIALLY when doing just a small plot. Simply flush with a garden hose, let dry, and put it up for the year. All the parts to the liquid fertilizer system are plastic or stainless steel. Less wear and tear on painted parts, less salts to corrode metal, and you don't have to worry about keeping liquid dry in humid or rainy weather as with dry. For small plantings, I've been known to mix up a batch of plain ol' Miracle Grow plant food and water. For bigger fields, it's a LOT easier, especially if there's just one man doing the planting, to transfer liquid via a small 12v electric pump, vs toting bags or shoveling bulk fert. into a hopper.
On the MF#39, I haven't used a dry fertilizer attachment in ages. (Just too much work when there's a better AND easier way, IMHO.) All it plants is pop corn and green beans. The beans don't get fertilizer and the pop corn gets side dressed after it's up past 3rd leaf stage. All my sweet corn, and the roughly 200 acres of feed corn we planted at my sons was done with the #71 and liquid.