Blenheim have bungee cord operate bomb-bay, so open with bomb weight and close by bungee cord force. No command is used, just drop the bombs.
Br.20 and He.111 have a hand crack operated bomb-bay, you need press an hold the key until the cycle are competed. Can be mapped in axis too.
Ju-88 (as far I remember...) accept toggle command... but one of many bug of this plane is, if you drop only one or two bomb, the doors close. Need open again to drop more.
Becomes unfeasible do "skip bomber" with this plane.
"Skip bomber" is not a regular form of attack in BoB, but is the preferred way online.
Sokol1