Get one of these:
{{gwi:376436}} (kiddie shovel)

and one of these (or similar):

{{gwi:376437}}

Fill up one of these with water:
{{gwi:376438}}

dump it in the tote, add your potting mix...mix with the shovel (yes, this is the actual way I do this...goes WAY faster)

Fill up your prepared jugs about 6 at a time. Make sure you have pre-cut vinyl mini blinds or other markers right handy to mark them as you go.

Sow, label, seal
Sow, label, seal

repeat at a mass pace...you'd be surprised how fast this goes.

I do my winter sowing like Mary does, assembly line style, wetting a large amount of mix in a large plastic tub, mixing with my garden fork, filling 9 jugs at a time. I cover my washer & dryer with old towels and line up the nine jugs on the dryer, lay out the seeds and labels and recording notebook on the washer, put one jug on a wire shelf that is placed over the double laundry tubs, sow the seeds, label, spray with water, cover top (I use the window method with a plastic bag rather than taping the top closed), put jug in an old dishpan of water to make sure mix is well watered, let drain on wire shelf over laundry tubs. When eight jugs are well drained I put four at a time in my laundry basket and take them outside. While some jugs are draining others are soaking in the pans. Doesn't take long to get in a rhythm and soon 30+ jugs are done, even more if I'm doing 2Ls.

Before starting to sow I have already filled in the names of the seeds in my record book and pulled the seeds from the large files and put them in a small box. Any left over seed is put at the back of the box. When I sow I just need to put the date and number of seeds sown in the record book. Also have marked the labels with the seed names so they are ready to pop into the containers.