I only inject in my stomach area when I want a fast response.
I've been injecting for 31 years, mostly either in my buttocks or skinny thighs, and I have no significant markings at all. (This is a feature of my prejudice: I wonder if pen-injectors could be to blame - I find them to obscure the injection site; I only ever use disposable syringes.)
If I were somehow magicked back 31 years, and with my diabetes know-how I returned to the work I returned to soon after first being diagnosed, then I swear I could work as a motorcycle messenger AND control my blood sugar as I do now.
I tested my blood sugar frequently then, just as I do now. (I mostly use visually read testing strips now, just as I did then.) And I ate frequently then, just as I do now.
But it's what I eat now that makes the big difference. I could not safely achieve typical HbA1c readings of 27mmol/mol (a non-diabetic normal) if I ate what most people eat, and if I ate in the way that most people eat - most diabetics included, if DAFNE and the likes of this forum are anything to go by.
I don't need DAFNE, and I don't need a pump.
And I don't need to 'count carbs' either.