the approach you have definied is good. As for how to deal with a brainstorming question, you should always identify MECE buckets first, and then brainstorm. In particular, quoting a previous post I wrote, the process could be the following:
- Recap all the information received until that moment. This will give you time without sounding you don’t know where to go.
- Always try to identify 2-3 key elements that would constitute the fundamental pillars of your brainstorming.
- After having defined the key pillars, start to brainstorm for each of them.
Bonus: you may ask for time after step 1 if needed, to think more on the appropriate structure to apply before brainstorming.
Let’s see a concrete example.
Interviewer: So, generally speaking, how would you decrease the cost of raw materials?
Step 1: Recap the situation
Interviewee: So, if I got it right, you would like now to move to the elements that could decrease this cost. If it is fine for you, I would like to do a small recap and then move through the key elements that can help to do so. At the beginning you asked me what brought a decline in profits. We have identified the problem lays in Product A, and in particular in the cost area. We then found out that the main increase in cost was related to raw material.
Interviewer: That’s right.
(Notice that you may have likely gained 30 seconds of additional time just summing up information)
Interviewee: Do you mind if I take 1 minute to think about it?
Interviewer: Please take your time.
Step 2: Present the key pillars of the structure
Interviewee: Thanks; I believe there are two key areas to decrease the cost of raw material; we may decrease the cost of each unit, or we may decrease the number of units we buy. I would like now to go a bit deeper in these two components.
(Notice that even if you are brainstorming, you are first putting down a list of the MECE pillars of a structure. This is fundamental to brainstorm correctly)
Step 3: Brainstorm elements inside each pillar
Interviewee: Well, in order to decrease the cost per unit we may do a couple of things, keeping in mind we want to maintain revenues at the same level: number one, decrease the quality of the units that we use; number two, negotiate with the supplier; number three, find another supplier.
In order to decrease the number of units, we may do two things; we may implement a more efficient method to use them, so that we would have to buy fewer of them. We may also substitute some of the units with something else that may be cheaper and with the same effect on the final product.
Of course, the best way to do correctly step 2 and 3 would be to have good structures already in place and/or have read a lot of cases, to backup your references.
Hope this helps,