In a large bowl, dissolve the sugar and then the yeast in the warm water. Add the milk, oil, salt and 3 cups of flour to the yeast mixture. Beat vigorously for 2 minutes.
Gradually add flour, 1/4 cup at a time, until the dough begins to pull away from the sides of the bowl. Turn the dough out onto a floured work surface.
Knead until you have a smooth, elastic dough. Because this dough is so slack, you may find that a bowl scraper or bench knife can be helpful in scooping up the dough and folding it over on itself.
Put the dough into an oiled bowl. Turn once to coat the entire ball of dough with oil. Cover with a tightly-woven dampened towel and let rise until doubled, about 1 hour.
Turn the dough out onto a lightly oiled work surface. Divide into 18 equal pieces. This is done most easily by dividing the dough first into thirds, then those thirds into halves, then the halves into thirds.
Shape each piece into a ball. For hamburger buns, flatten the balls into 3 1/2" disks.
For soft-sided buns, place them on a well-seasoned baking sheet a half inch apart so they'll grow together when they rise. For crisper buns, place them 3" apart.
For the second rising, cover with a towel and let rise until almost doubled, about 45 minutes.
Fifteen minutes before you want to bake your buns, preheat your oven to 400°F. Just before baking, lightly brush the tops of the buns with the egg wash and sprinkle with whatever seeds strike your fancy.