How to start with personas for internal use

Im wondering what is the best way to introduce personas and how to start the general workflow.

I work at a insurance company as a UI and UX designer, the people in the company use internal application for most of the stuff they do daily.

Before i came to the company, the developers "designed" the applications and over the years the employees got really frustrated, thats why they hired me as the start of a design/ui/ux team.

Since working for internal people is new to me, im wondering whats the best way to start a persona workflow in my company? There are many stakeholders from different departments (for example: car insurance department, life insurance department etc.) all of these people will work with a single application since one of the company scopes is to merge over 49 (!) applications into one application.

I thought the best way would be to get to speak to everyone of those stakeholders and interview them about what frustrates them, what is wrong with the applications they work with now and what they wish for the future and take this as a basic scope to construct the application.

How would YOU do it? I have a freedom here, budget is kind of limited but the time of the stakeholders definitely is, thats why i want to interview them as short as possible with the best outcome and from there on create personas that i will communicate to the developers so everyone has the same users in mind when working on this new project.

Tipps and Tricks are really welcome.