I've used 3D models created in 3rd party modelers but the uv mapping theory generally is the same for most 3D packages. Once the model is complete it can be exported as an ".obj" file which is a non-proprietary format and an industry standard which most 3D packages can handle.

I've often used UVMapper Pro for models I was going to use in Bryce and other rendering engines. UVMapper has a free classic download which works pretty much the same as the Pro version and will suit most your needs. As with most mapping packages the user has to decide which type of mapping format will best suit their needs when they first import their mesh model. In the attached image I show how I uv mapped my rendition of the Viper Mark II Battlestar Galactica Fighter which was rendered in 2009 using Bryce. Some models are easier to map when using Box mapping, like I used on the Viper fuselage because you can design (paint) the bottom, sides and top separately on the same template. On the same template also together with the box format I used planar mapping on the cockpit control panels of the ship and a planar split along the Z axis for the pilot's helmet and pilot. It is best to divide your model into groups such as; fuselage, control panels, pilot and helmet as in this case so that you can separate each element and move them around the template so that it would be easier for you when you export the finished template into your imaging editor program. Same box mapping was used on the F-16 model rendered in View. These renditions and others can be viewed in larger resolution in my gallery.

UVMapper tutorial and download pages;

http://uvmapper.com/tutorials/tutorial_classic_win.html