If it's any item that remotely resembles the destroyed items in the game, I'll use the destroyed shapes (accessible from the hidden menu).
For other items, such as ships, in the following missions, I will have the item re-attacked before the player gets there.
For default items, especially airports, the best thing to do is overlay the item with an identical item on the exact same spot. The easy way to do this is dig into the .MM file, copy the location and bearing of the item, and paste that location to the replaced item. This saves you time by not having to do it in the game and trying to "line up" the item via eyeball.
For 3D items (i.e. Bridges), this trick may not work. Instead, the game will stack the items on top of each other.
Be advised, with using the "friendly sides" menu, your aircraft may still not land on the now-friendly airport. I ran into this problem with the Baltic - USSR campaign. To fix, I had to overlay a friendly airport.
Another option is to create several maps showing the progress of taking territory. Just make a copy of the .MM file, rename it, go thru it using Wordpad, and change Nationalities that way. You can also add and remove items as well. IF you chose this option, do it BEFORE building missions. Otherwise, you may run into problems with two items sharing the same Alias number.
The last few campaigns I built, I kept a list of scenery items I often used in a text file. This way, I could copy/paste the items into the .M file. This trick saves a ton of time. Likewise, as in the case with my Vietnam map, I find it best to delete many of the default items off the map.
http://myplace.frontier.com/~usnraptor/Fighters%20Anthology/Maps/Vietnam%20Scenery.txtBe sure to check out the tips in my http FA folder:
http://myplace.frontier.com/~usnraptor/Fighters%20Anthology/Misc/If I haven't been clear, or didn't answer a question, feel free to ask.