I think as others have said, that idea itself may not be quite right and you are looking to us to brainstorm. However, I do know someone who does exactly this, for free. He makes his money by facilitating the ability of others to think outside their proverbial boxes, using what at the core, is basically workshop facilitation. That's an easier sell than 'professional ear' as the market is kind of there already. You don't have to know much about the business to facilitate a workshop or coach per se, as you need to concentrate on the facilitation. Many people like me can't think and facilitate at the same time. :-D Especially if you're too close to the problem. So effectively you get called in ad hoc to facilitate workshops to allow all the firepower in the room to concentrate on the problem at hand. It doesn't mean you can't structure a session where you give advice at certain points or when asked. However, that risks exposure. You can always help by researching after the fact, where the team has found key questions they want answering. Write them on a post it and take them with you.

If you become a millionaire off these ideas. I'll take 10% ;)

Candor and modesty are undervalued virtues. Especially in the startup scene, where ambition, optimism, and "rounding up" are thought to be necessary & sufficient character traits for success.

You've been quite candid about what you perceive as your weaknesses in this area: (1) lack of experience and (2) not being well spoken, as you put it. So I think you deserve an equally candid answer from me.

I don't think it's realistically possible to start offering a paid service as a brainstorming facilitator unless you already have (1) a network of people who rely on and pay for your advice; (2) some significant credentials or accomplishments to point to and entice customers with; or (3) an unusually charismatic stage personality.

In my city, there are plenty of psychics and spiritual healers who get by on charisma alone. Quite literally, I sat next to a guy last week who claimed to be the reincarnation of John the Baptist from the 7th dimension. No joke. He was doing a session with a lady at Starbucks.

Do you need to be as compelling a speaker as him? No. But before you can begin charging, you need 1 of the 3 things I mentioned.

In the mean time, you can volunteer your time to acquaintances, network with the local startup scene, or help people online. Gaining experience reading is useful. But try actually launching a small startup project in your spare time. That will be an invaluable experience; and to the extent that it succeeds, it's something you can point to.

For the record, I think you're "well spoken" enough. So don't let any insecurity there hold you back. Just work at what you enjoy. If that's helping people brainstorm ideas, then try it. Just don't expect to be paid until you've accumulated relevant experience ... or people start offering to reimburse you for your time.

Right now, I don't think this idea is ready. Here's why: It's ironic that someone who wants to get paid as a brainstormer is asking other people to do his / her brainstorming for free!

-Start!! Offer free sessions, make changes and collect feedback/testimonials. This will also allow you to develop your skills, Once you are confident enough you can start charging for fees. If you cant answer questions, research and get back.
-You mentioned lot of "i think" 'I believe" maybe its time that you start and having solid understanding of what you are capable of. Definitely join toastmasters.

Several friends have launched business incubators in my city. Network is key. Personal brand is also important. If you need some advice on how to position your brand to attract valuable connects and reach entrepreneurs, let's talk!

Starting a service business is much like starting a product business. You need to validate your idea. It's great that you are talking to beginner entrepreneurs. Sounds like you are a good listener. What are the common pain points they mention to you? Can you build a service offering around that? I would go through the similar process one would do to validate a product idea. Create an Initial service offering landing page (after you have a good understanding of their pain points and a solution), offer a free consultation and some good advice to their problems then pitch your service offering. If they don't want to purchase, find out why. Do you need to adjust the offering etc.

As with any business you have to figure out how to position what you offer in the marketplace and the value proposition. What is it that you will provide people for payment? If you enjoy talking to entrepreneurs I would suggest going to Meet-ups in your area targeting that group. It would be a great place to get feedback on your sales pitch and get a better understanding of their needs. In addition, you could start your own group targeting those folks. Also, many incubators, co-working spaces and formal professional organizations have meetings open to the public where you can talk to entrepreneurs. Just like any business it comes down to offer, sales and marketing effectiveness. Best of luck!

My firm actually is starting an idea validation as a service https://vencosba.leadpages.co/validation/
just for this purpose.
It's a step up from the excitement of brainstorming and getting into the cold hard facts to see if the idea is wanted/needed in the marketplace.

Think tanks are fun but they can be pretty unfulfilling without structure.

I also have a startup lab www.thelightsonlab.com where we do this from think tank to launch all in house and privately funded.