gameplay4filmmakers

Filmaking can be much easier when speeding up gameplay and using cheats.
Why playing the game at all? First it's fun and second you need to play through the missions to get access to all the areas of Liberty City (Bohan, Algonquin, Alderley). Of course you can access those areas while using multiplayer maps but that is a different story.
So until there are no 'saved games' available from others and could be used you have to play the game at least to some level.
What helps is using the cheats available in the game. The cheats acivated by typing special phone numbers in the phone. Later you can use them from the cheats menu of the phone.
The most important one are to get health, armour, weapons, cars, bikes, helis, and to change the weather. Yes, you can make a call (to whom?) to change the weather :).
List of cheats
(Those are for Xbox, but will work for PC as well)
I've used those to speed up work for my GTA4 movie Liberty City a lot. Although this movie didn't depend on using any cheats it was very handy to use them. Having a car, bike or heli ready when and where you need it was great help. And changing the weather was useful as well. Not to talk about getting rid of the 'wanted level' when you accidentially hit a police car or shot people too much while shooting your film.

But be careful, using cheats will disable soem achievements in the game you need to get to complete the game at 100% for

Using a taxi during the missions helps speeding up gameplay as well. You can instantly go to the destination by paying some extra fee. Even better after some missions done for 'Roman', he'll send you a private taxi when calling him for this service. That helps, because it's often hard to hitch a ride with a taxi in remote areas or exactly then when you need them. And it saves money as well.