@deborahh I'd suggest watching out for local pollutants before dropping seeds. Areas with a lot of traffic, car or foot, will be very unfriendly for germination and growing. Areas frequently sprayed with herbicides, flood prone, salt build up (road salt or runoff from fertilizer). Places that used to be/ are near chemical/ waste heavy spots (oil change, mechanic shop, restaurants, more)
Not trying to be negative! Just don't want you to waste effort. Seed bombs are great, but work best in areas already friendly to growth. Most barren spots are barren for a reason; if I'm reading the OP right, that's what you're focused on.
If I missed something, or if I'm saying something you've already factored in, I'm sorry; I can get opinionated sometimes. :) don't let me discourage you!