Sky4Sim uses a virtual keyboard, which I personally don’t like. Both FSKneeboard and the InGamePanels I linked to in my previous post use a “freehand” notepad, which is a bit more practical.
You’d still need a mouse to draw or write and I also find that a bit awkward, but you could use a pen mouse. I haven’t tried it myself, but from what I’ve seen online it basically writes like a thick pen. You can find them online for around £20. Or a graphics tablet that comes with a properly sized pen for around £40.