Here's my (someone else might have done it before) "atomic build order", I have found it 99% effective for a fast win on small to medium maps (maybe larger?)... you still need to know what you are doing against a player that can out last your initial rushes with towers... few conditions though: starting oil needs to be quite high and the longer it takes for you to harass your opponent the more chance he has of getting ahead of you (ie if you are separated by scavs this is probably not a smart build strategy). Oh for 2 truck start (instead of 4) I normally build a factory first and then produce 2 trucks to make 4 and then continue as normal:
RCFFFF then split trucks so two for Oil refinery and two for Derricks
Res MG all the way to mk2 upgrade
Soon as C is built design mg wheels unit
As each factory is built start manufacturing mg units
When the four trucks finish the last factory split them to derricks and Oil refineries
YOu must do all this fast and efficiently, no pauses between building/res`ing, every thing must flow or you can find yourself up sh*t creek.
After that you go which way you want... many times the game will be over in less than 5 minutes
You should have quite a few units by the time you look like getting low on oil + you will probably have two oil refineries and some derricks by this time.
the main thing is to spit out mg units quick, once you have 4 or so head straight out truck hunting... if he is not mirroring this (ie being able to defend against mg units in around 2-3 minutes) your will find him with his paints down
I always smash nullbot like this and have only been beaten by exceptionally cunning MP players (or those that know beforehand what I am going to do)... your run of the mill MP will probably not give too many problems - more likely he will GG or rage quit.
Disclaimer - there are many different strats for many different maps, this is just something to play with