When the ground gets to hard to work with a trowel, you can take a regular sized sledge, mine has about two foot of handle and then pound your bowl in,I then pour a layer of peat moss and spray with glycol,bed the trap, i spray the working parts of the trap out of habit more than anything else with glycol at this time ,then cover with more peat and again bed the peat as solid as possible and another squirt of glycol, I finish the top with a thin coat of dry dirt and another shot of glycol.
if its a flat set you can take your sifter and scoop undesturbed snow (make sure you dont handle the snow with your hands, my father use to use the bottom of an old canoe paddle to handle the snow)and give the set a sifting, if you feel the snow is going to crust on you, give that a shot of glycol also if you want.
if you want a dirt hole or holes use a rerod or a bull pin and pound them where you want them. if you want an old fashion post set pound the hole out with the rod for your post and insert were you want it. probally not the best system out there, but it works for me. good luck... Jim