Do not upload 2 times the same file.
Check the SHA1 or whatever you want with the cloud but do not upload several times the same file.
Take a look to Wuzzup, is similar to Comodo CLoud Scanner, also free but much better.
You can download it and try it for a couple of days and you will get many good ideas. http://bugbopper.com/Wuzzup/Default.asp
A way to send a file to Virus Total in the interfacel, right click - send to...