I will disagree with the statement that they should do only one drug. If they have been lifting for a long time, consistantly and have made noticable progress, then running a moderate dose of test with deca and dbol will work great.
I don't care if you are a newbie or a pro, you will lose a certain amount of weight after a cycle even with a proper diet and training regime.
However, they all need to understand that if they do not bust ass on the cycle be one drug or multiple, any gains they make will be false gains.
It is a matter of personal preference as to ones choice and all we can do is guide them in the right direction intelligently and not by insulting them or degrading them. We were all newbs once.