This is for the Point of Contact map and probably others).
As you get past each barrier hive you will have unlimited time to search the next area.
Take trophies from the first area and carry them into the next, hide them close to the next barrier hive. Later, move them again to the last area so you have trophies where you need them most.
Go back as you open each new area to the previous one. Grab a flare, bring it to the new area, swap it for a found trophy so that the flare is now where you found the trophy. Set the trophy down at the barrier hive (or where you wish to use it at the end hives), go back as far as you can, get another flare and repeat.
This way, all of the unneeded flares and trophies found at start can be brought to a more useful position in the game.
Hypno-knives and flares can not be traded for a set-up trophy, only ones still in their 'found' spot, still lying on the ground. So, make sure your equipment slot is empty as you finish a barrier hive so you can pick up/move trophies forward and then come back, get flares/knives and move them forward, trading for found trophies in the new area.
Set 1 trophy at the corner, by the army vehicle just after the first barrier hive, for the end run home as you will be getting shot by scorpions there. You can do this as soon as you beat the hive, the trophy will stay until the end of game (there may be an upper limit to how many you can set down which could effect this, however, in solo, i have had six at a time set down with no issues).
Be sure to leave a flare on the ground near the barrier hives so it can be easily grabbed and used on the run back to start at the end of the game, this helps a lot (as these places get temporarily blocked by meteors on the run back). Only the spot mentioned above (where i said to drop a trophy) by the first barrier hive really needs a flare for the run home, so try to leave one that can be grabbed for that area at least.
Only the time from that barrier hive to start effects whether or not you get a platinum escape, so you want to have that battle under control at all times. By having the trophy/flare ready, you should be fine.
Other speed boosts for last run:
Playing as medic.
Holding pistol in hand with at least 1 skill point in it.
Not deploying boxes, fighting, throwing grenades.
All of the above at once.
Simply run. (though if fast enough, or ahead of the rest, players often dump anything to get their 'spend rates' up).
[more cheats for Call of Duty: Ghosts here]