Here's my flow thru plastic barrel. I used string trimmer line for the grate, spaced 1 1/2 inches apart. I may have pulled too hard because the line tension made the middle of the barrel deflect a bit. Next time I'll have to fit a pipe brace or something across the middle to hold it round... or something. The occupants shouldn't mind though. I used low tech leather and sheet metal screws for hinges. This door may change in the future since I'm anticipating leaving it open most of the time for air flow, and think I'll need a screen door to keep out critters.
I loaded it two days ago with the top 3-4 inches of my wooden bin, and fed them a mix of vegis, coffee grounds, and rabbit manure yesterday. A plastic garbage can lid fits ok as a lid, but I think the wind will blow it off. May have to make a plywood circle. Added a piece of yardstick along the inside to measure the fill rate. I'm guessing that noting the height monthly will show some growth.
It is in a shady spot but since it's a white/clearish barrel I'm wondering if light will get in too much and keep the worms underground. May not be an issue. I'm also thinking that I'll make the bin portion a little deeper than 18 inches like maybe 22 so there can be 18 of bin with a 4 inch air space on top. I'm a dependable supporter of life's most constant thing... change!
Now I get to run the material left in the half of my wooden bin I took the starter layer from, through my trommel screen I just finished.