No i am not using too much proxies, i am just using 5 public proxies which are found Good by Scrapebox from above your lists. I just did a fast posting on 335 URLs and able to post successfully on 88. It is almost 33% success rate even then I think it is ok for my first attempt and also these links are from my competitors links so most are from very high PR.
What else you will guide to get much higher success rate using public proxies? And also any good Scrapebox Tutorial you will recommend?