Is there any Art supply store nearby that sells Brushes, paints in Nanjing?

You can buy them at the New China Book Store which is located at no.56, East Zhongshan Road, Qinhuai District. You can take metro line 1 at Shengtai Road Station to Xinjiekou Station, Exit 24. When you get out from the station, you just need to walk eastwards for about 110 yards (100 meters) to the book store.

Thank you Nick. Will definitely go today to check it out. It's so pity that all my earlier trips I had stayed in the city center Crowne Plaza which is actually a stone throw away from the bookstore you described! But as they say - better late than never.