Thank you, Mr. M and Clive for your responses.
Yes, it makes sense to say that by using 'hold' and 'different', I have made the word 'discussion' countable -- Good. I wil further study that, but I think I have seen some cases where the context is somewhat set like the above situation wherer both 'hold' and 'different' unfolds the action countably, yet the resorting to uncountable usage has still prevailed.
I think it might be better to make it less straight forward like this:
Different discussion on this topic might not be the suitable way to go about reaching any kind of agreement; I think the best way is to hold a single discussion on the matter tomorrow morning with all the concerned parties in attendance. How about it, gentlemen. Would you go for my idea?
As to no 2, I would change like this:
Yesterday, I and my roommate went shopping together to buy soap and found there are a lot of brands of soap in stock in the market. Aftr looking at the choices, we forewent our usual brand of soap and two other brands of soap, one in the yellow package and the other in the blue package, both from different makers.
I am home and trying to wash my hands and upon realizing, there are two brands of soap on the sink, I tells my roommate this (I think the sentence I wrote originally contained tensical mistakes. Do do you agree?):
1. Hi, where is a soap in the yellow package we bought yesterday? Let me try that one.
Or does it have to be this?
2. Hi, where is a brand of soap in the yellow package we bought yesterday? Let me try that one.
If no. 1 doesn't work, can you give me one sentence where the phrase 'a soap' will fit right into?