to get the speed of jason mc donald trophy follow these advices:
don't try to achieve this on your first walkthru. Better start a new game after you complete the game a first time. Set the new game on easy so the bosses offer less resistance (less resistance = less time taken to kill them). Yes it sounds like a whimp, but this trophy it's not about being tuff; it's about TIME! So it's better to kill Ares in less than 5 minutes than 10; EVERY SECOND COUNTS, THIS IS FOR REAL! Ending the game after 5 hours 0 minutes and 1 second doesn't give you the trophy for making your best try; it's 5 HOURS OR LESS OR NO TROPHY, PERIOD.
Don't start looking for chests. If you start the game on easy it won't be too necessary to increase your health bar (collect gorgon eyes). Collecting chests will distract you, so don't
Before you enter the desert of lost souls (the part of the 3 sirens) check on youtube for a video about it so you can get an idea where to find them quickly. This part can make you lose LOTS of time if you simply star wandering around without finding any siren. Extra tip: the first one it's in front of the palace, and no other siren appears until you kill that one; so go straight to that one before you start lookin for the other 2
Choose your battles: DON'T FIGHT UNLESS IT'S NECESSARY. There will be enemies on the way that are simply ON THE WAY, and you don't need to kill them to reach a certain point. There are fights that of course you need to complete to advance to the next room or to activate something, those you cannot avoid; but if there are a couple of guys just in the middle of the road, simply keep walking. If you set your game on easy enemies cannot hurt you that much so you can just ignore them even if they try to attack you; if you decide to fight every single enemy on the road YOU WILL JUST BE LOSING PRECIOUS TIME!
Try to start the new game soon after the last time you completed the game, so you have a fresh memory of where to go; that helps a lot. If it's been a while, then check out youtube or something to refresh your memory so you don't have to wonder where did you have to go next
Don't waste time on searching for treasures, Again, DON'T LOOK FOR CHESTS! That's the biggest waste of time you will have during the game
I know some people say to use the cow costume, but there are 2 problems with these: first you will have to defeat the challenge of the gods (which it's really tuff but not impossible) and second, I think that if you do use the special costumes you don't get trophies. I'm really not sure about this, I got the speed of jason trophy using the regular kratos (just to make sure, I didn't wanted to spend so much time playing to find out they won't give me the trophy for using a costume)
Finally: don't look for chests and choose your battles!
I lost a lot of time on the desert of lost souls, and barely made it under 5 hours (4h 59m). If you still need the Seeing red trophy (the one for maxing up all magic and weapons) you will have to choose which one it's more important since you cannot achieve them both at the same time. Getting to much red orbs requires time (especially if you go for the infinite red orbs glitch),time you don't have, time you will waste if you try to beat the game under 5 hours; so it's one trophy or the other
I hope I can help you. God of war 1 became my first platinum trophy (just a couple of weeks ago) and then I completed the God of war 2 platinum trophy. I'm not too much of a trophy hoe but even if any trophy looks tuff, there's always a way to get them and that's trying trying trying and trying and if you fail, try try try again