Considering the speed - or lack thereof - of those huge transport ships, carrying a factory through more than one or two systems becomes tedious. I was wondering if there is a way to transport more than one factories at once. I thought about hiring multiple transports on my way to the shipyard, but as far as I can tell I can still only buy one single factory - I do not seem to be able to use the other transports...
I experimented a bit and found something useful:
When purchasing factories from the shipyard, only one transport ship in the sector will be used. That means that you cannot hire e.g. two ships and buy two factories at once - the second transport will not be used.
However, if you manage to get the ship that carries the first factory on its way to one of the next sectors by traveling there and waiting for it, you can quickly skip back to the shipyard, hire another TL ship and buy a second factory.
The trivial way to use this would be to bring a hired transport from another sector, use it for the first factory, get it to the next sector and then go back, quickly hire the local transport and buy a second factory. Timing is a bit critical, so having a docking computer should allow you enough time for your shopping spree before the first transport follows you back.
Alternatively, if you wish to bring multiple factories from different races to a location, you can select a route that goes through the shipyards and just hire the local transport in each case - under normal circumstances the other transports will be lagging behind you so the "one transport per shipyard" rule is not violated...