Ohh, wow time goes fast, maby things have improoved i hope.
I was simply using Gimp with the BIMP plug-in, but yeah i'm afraid i had to redraw the pinklines manually because if the pinkline got slightest opacity or blur-damage because of the upscale, that not good because there is only one correct pink says someone
If you do one theme, you will get pretty fast, so fast so you might as well do a couple of more, but yeah, best motivation speech i have atm
Just start playing with one image and experiment and you will know what needs to be done should you go for it, and i think scaleing 150% sounds like a bad idea (result), see for yourself, try stuff and BAM! new hobby