I have made a save for people using Xploder that unlocks the biggest grind trophies.
So far I have done the following:
99,9999 XP (War Veteran)
249 games (Topher Would Be Proud)
249 Wins (A Winner is You!)
Viral Trophy (Red Faction Member)
4,999 Kills (Courier Of Pain)
Play a matchmaking game and win to pop all these trophies.
You will also get the 3 wrecking crew trophies with this save. Play 1 rould to pop all.
ZIP Contains EU & US
If the folders appear empty, you will need to show hidden files on your PC.
Glitchboy has also uploaded a US save to the Xploder database that will unlock the challenge trophies. RFG will unlock them in a random order, so if you are looking for them to look legit, you should first work on the easiest 8 challenges.