sand blasting is the best and better results than any other procedure. wire brushing will only make the area shinny and will not get into the pores. Chemicals will smear the area and make it look worse.
No comments or suggestions from me other than blasting.
If you have a compressor, a sand blasting kit is real cheap and the sand is cheaper. You could even rent the system and do it yourself for a rental of about $60 and the purchase of the sand. I would really consider this.