Is definelly worth, the best item you can use is exp share, untill you can't get him, you should aways lead the battle with the weakest, aways rotating them so the strongest and the weakest have a minimum of 3 levels more than each-other.
Of course, this rule has exeptions, such as gym battles, gym trainers, elite 4, etc.
After getting the exp share you can lead with any Pokemon you want and just rotate the exp share around them instead, aways making sure that they are well balanced in levels, such in difference of 3 or 5 levels for example.