You will get this long before the Keeper of the Armory Achievement - all weapon challenges. So if you are going for that, do not worry about boosting this separately.
In a 15 min match 1 vs 3 you should be getting around 20k minimum (depending on what weapon challenges you are going for) plus any additional xp for challenges completed. This is by far the most efficient way to get this if you also plan on getting the Keeper of the Armory, otherwise one of the other solutions would be better suited for you.
To give you an idea on potential xp earned with more people in a boosting session - I had an 80k round for 1 vs 5 --- 499 kills and completing both Power Axe and Thunder Hammer challenges all in one 15 mins round