Help, I am trying to redo my back porch, carport floor and driveway ...?

I have started redoing the floor on the backporch, carport and the driveway. The porch and carport had carpet and the drive way is concrete with paint... I took up the carpet and applied an adhesive remover and scd all that up , and then used a cleaner degreaser but there are still a little paint on there and before I use the acid echer, I wanted to make sure that it will be OK, to leave a little paint on there as long as it is smooth.. I have removed as much as I can get off.. even by scraping with a razor scr.....The the steps say use the acid echer and then primer and paint.. Well .. my question is does every little bit of paint .. down to the concrete have to be gone.. Or just sc up what the cleaner degreaser loosened and use the acid echer and primer and paint?.. I have done ALOT of work on this project and spent alot of money on products and want it to turn out nice... Any advice would help .. Thanks ... signed ...sore arm and back... ?????