Using transports

[NapSpan]

Well, I really want to be able to move my troops around with them but i have some questions (I only play UEF).
When i should use "assist" command in factories and when ferry?
With ferry i can load already built units in those transports but if i lose one, i must make again the ferry order if i want to replace the dead transport.
In the replay, I use a lot transports to take advantage and it worked, but after all my enemies had little to none air coverage and I am 1200, this kind of gameplay style is still viable in upper levels? (Using mobile aa in the drop zone and inties to protect transports)