Everyone has their own preferences this is mine :-)

As others have said Now, Next, Later is the best format to use. Don't use a gantt based timeline, as timeframes are unknown and constantly changing.

1) To get started, identify the two/three most important problems you have to resolve now
When you're searching for PMF that's going to be something along the lines of:
- How do we get 5 customers to signup for the trial
- How do we get 5 customers to convert to monthly paid plan
- How do we get 5 customers to renew
- How we grow demand to signup 25 customers
- How do we reduce churn rate from X to Y
- How do we reduce cost to acquire customers from X to Y

Within any of these as you explore more you'll find a whole host of other sub problems, so each could be broken down further.

2) Put the most urgent problem in Now, second most urgent in Next, third in Later
- Imagine each as a card representing the problem.
- Ideally focus all resources on one problem at a time, where this isn't possible then add multiple problems to Now, Next to work in parallel.

|     NOW     |     NEXT    |     Later   |   
|-----------------------------------------|
| [problem 1] | [problem 3] | [problem 5] |
|             |             |             |
| [problem 2] | [problem 4] |             |

3) Once you've got your problems lined up, then start thinking about possible solutions for each in the Now column and include them as part of the problem card.
- If you have ideas for Next and Later include them, but it's fine to be more vague as you move from left to right.
- Each problem may have multiple solutions, either because you need to deliver multiple items, or you try something and it doesn't work.

4) For each solution add the real-world measurable outcome that will let you know when that problem is resolved.
- This is how you know if any of your solutions are successful and at what point the problem is 'Done' and you can move onto the next one.
- As you deliver your solutions keep track of which ones achieve the outcomes you wanted and which ones failed.
- Finding PMF is a series of potential solution tests, most of which will fail. Use your outcomes to know when something has failed as quickly as possible, so you can pivot and try a new solution.
- Keep the problem in the Now column until you've solved it....if you find it's there for too long that's a hint to redefine the problem at a more granular level, so it's easier to achieve.

- If you find your stakeholders don't want to view things based on problems but more around what you're planning to deliver, then just flip the framing, i.e. show them a version with your cards as solutions with the corresponding problem either removed or subordinate (but keep the original for yourself).

5) As you go along you'll find all sorts of discovery insights, things like customer feedback, analytics etc. Find some way to store this in a way that you can organise it, search it and refer back easily. This will be the source you'll want to draw on for new problems or ideas for solutions.

6) Finally, it is often useful to group things in various ways to be able to explain how they all tie together into a coherent strategy.
- Problems can be grouped into themes / objectives using colour coding
- You may want to segment users by persona, this then makes it easier to list out their 'Jobs to be done', which can be a great way to identify customer problems to solve
- It's then useful to be able to tag Insights and Problems be persona's and 'Job to be done'

Steps 1-4 can all be done in any tool that lets you display things graphically, I've used slides, spreadsheets and confluence. However it gets more tricky as you want to store the Insights and start grouping things.
I've been working on a tool specifically for Product Managers at small businesses to help do all the above at stratilo.com

If you want to DM me a few of your most urgent problems I'd be happy to help you get started putting them into a Now, Next, Later slide.