Some might approach it differently but I NEVER do mock-ups in any photo editing software. Ever. I think it is unhelpful at best. I will perhaps sketch something on paper… but that’s it. I literally open up a text editor and just start coding.
I still think mockups are important, especially for explaining to clients the approach you took in regards to UX. I can see this working for specifically development but for UI and UX purposes, not so much.