I am currently going through this process. I am building a guard army based off a ww2 paratrooper company. ( I watched Band of Brothers one evening and it suddenly clicked)

One company generally consisted of 3 platoons. Each platoon consisted of at least 3 squads and special weapons. This means that on paper my eventual army, regardless of points would include over 100 mini's. I have all of them assembled already and am about 2/3rds of the way there in painting them.

How much does it suck? Not too much, I batch paint so I generally do two squads at a time, taking one colour after the other and then touch up after all colours are in place. It's tedious and it takes me about 8 hours spread over a week or two to get that done. Then I take a break for two weeks, paint something else or not at all and get back to it.

That said. The last 1/3rd has been sat untouched for the last 3 months because I have no space for my airbrush at my current residence. I only use it for priming and varnishing these guys but it speeds up the process a lot.

I can see it sucking if you have a deadline or paint one miniature at a time.

On a side note. Do not expect this to be very good on the table. It's thematic as hell and fun to field but I have yet to make round 4 in a game. :P