Yes, FirmwareSender works with them the same way as patches (there's no difference at its level). But I'm pretty sure that it doesn't read from device slots, there's just no support in current MIDI protocol for that.
Btw, there's also integration in OwlProgram for uploading resources now, you can use something like
make RESOURCE=/path/to/resource SLOT=SLOT_NUMBER resource . Resource slots follow patch slots, so 42 would be used by settings and you can write your own data in remaining 11 slots.
If it works correctly, new firmware will show upload progress bar and you will see new resource in resource browser page. You can also delete from that menu after clicking on it to enter delete mode. And resources that start with double underscore would be write protected in that menu (but can still be overwritten).