Some factory stuff might be of use to new players:
If you stuff your factory with a load of combat blocks and devices (such as the free devices from the Xmas advent event), the BP (blueprint) spawn time will be drastically reduced, probably to 0:01.
However, sometimes the factory is a bit too full, it already has enough for the BP, and it won’t accept any more devices, so you can’t reduce the spawn time. Here’s a short guide how to get around that …
(1) Make a note of how long your BP needs to spawn.
(2) Change the BP in the factory to something huge like a Class 7 BA or CV (you can get these off the workshop or knock one up in Creative). Note how long the large BP takes to spawn.
(3) You can then stuff the factory with more materials and devices. Even ammo or old motorbikes can reduce BP times.
(4) Do this and reduce the spawn time by the amount of the time needed for the BP that you actually want to spawn.
(5) Then switch the factory BP back to the smaller BP.
(6) The spawn time reduction is “banked” and will apply to the next one thing that you start building, even if you change the factory BP before starting the build.
So any smallish BP can be spawned in 0:01, even if your factory is fairly full already 
Caution : Stopping a BP that is already in progress counting down, will lose this spawn time reduction