Can a 8 month old guinea pig be introduced to a new one?

I had to do this a few months ago. What i did was put the guinea pig i already had in the run on the grass. I then got a washing basket and turned it upside down and put it in the run with the new guinea pig/s underneath it. (hope that makes sence) The washing basket had holess so the guinea pig that is free in the run can sniff the new guinea pig. Watch what the reactions are are keep and eye on them. My 4 guinea pigs get along fine but it's just pot luck!!! Hope this helps.. Leave me a message if you want any more advice..... Laura