thanks a lot guys, I did a bit of internet-research, so I went confidently for acetone and it worked very well. However, the acetone I have is probably a watered down version, it's a "nail polish remover", but the smell is milder than the acetone I used to have. After I use it a few times, I couldn't see the marks of the residue, the paint also went off, but if I slided my finger on the pan, I could notice it was still "adherent" (not a lot, but noticeably so.) so I went on to the next plan: cover the base with vegetable oil and leave it until tomorrow.
Does anyone have any other alternatives / suggestions for what to do tomorrow after rinsing the oil out? should I leave it on heat for a while, etc?