Here in the states oxalic acid is cheap and easy to get. I never get any discernible residue or gritty surface with my method (soaking, not brushing on). I'd rather have a safer powdered form of acid in my darkroom than a bottle of liquid HCl. I buy oxalic acid in relatively large quantities because I also use it to make potassium oxalate developer for a fraction the cost of buying potassium oxalate. Cheap, safe, effective, NO grittiness. The end.