In video editing there are two basic and essential actions: divide them into smaller fragments, and join them together again.
For this job a tool like 001 File Joiner & Splitter is very useful. It lets you both split and join. You can split any video file (with a maximum size of 2GB) into smaller and more manageable pieces, so you can work on them individually (and to make them easier to identify, the program numbers them).
When joining the fragments together again (to create a new, compact file) just collect all the fragments you want together.