I make IP scans.
I scrape public proxies and test them to keep only Google Passed.
Then, with ProxyFire, I filter these proxies to keep only one port (example : only 8080, 3128, 8909, ...).
Then, always with ProxyFire, I will generate IP ranges from these proxies and start scanning.
Finally, I will test proxies obtained with ScrapeBox.
This method is extremely powerful, but can take time.
The hardest step is to find good ranges, to not waste your time...
ProxyFire (free/paid) :
Code:
http://www.proxyfire.net/forum/showthread.php?t=33
Proxygo is the king of scan.
Hope it help
Beny