We've been using the slightly modified HISCO codes from VI History, which included levels of specificity that do not exist in the published version of HISCO.
For example, we have
1) a bunch of Managers (Cement Works, Gas Works, Lime Kiln, Mine, Powder Works, Sawmill, and Tanning Company) that *could* all be placed in a more inclusive category, like 22620 "Supervisor and General Foreman (Mining, Quarrying and Well-Drilling)"
2) 50ish posties (postman, postmaster, assistant postmaster, expressman, post office assistant) that could possibly be placed in the Mail Distribution Clerks category (37000-37090) but are listed as 35210, 35211, and 35910.
3) 8 store managers that are listed as hisco 40020,40030,40032, and 40033 but could be handled by the 21000-21990 range
4) auto salesmen/dealers that are listed as 48000, ticket sellers listed as 49090 - TO DO: what to list them as?
5) steamship pursers listed as 50040 - TO DO: what to list them as?
6) housekeeper, stewards, etc listed as 52020,52032, and 52040 - TO DO: what to list them as?
7) gentleman farmer, farm manager, and gamekeeper listed as 60040, 60030, and 60020 - TO DO: what to list them as?
8) hunters listed as 65000 - TO DO: what to list them as?
9) foreman of various descriptions listed as 70000 - 70150 - TO DO: what to list them as?
10) 1994 funky ones (X0000, X0010, X0015, X2000, X2280, X3010, Y1100, Y1105, Y1123, Y1125, Y1200) that correspond to mostly soldiers, gentlemen, cutters, and assorted oddballs (illegible, trailing ?) - TO DO: what to list them as?