Some professional microstock photographer using outsourcing service such as isyndica or lookstat to taking care their uploading process to multiple agencies, but you can do it by your self by using good FTP program out there.
Uploading to many agencies need so many work, then I tried many FTP program to achieve outomate uploading to multiple agencies and finally find PyroBatchFTP , I love PyroBatchFTP program because it's uploading to multiple agencies even when I sleeping by using scheduler feature.
Here is step by step how to use PyroBatchFTP.
1. First, make script with text program and save in C:\Program Files\PyroBatchFTP\Scripts and save as .cmd here is two sample:
a. Connect "upload.dreamstime.com", "username/ID", "password"
LocalChDir "C:\new_upload"
RemoteChDir "/"
PutDir "*.jpg"
Disconnect
b. Connect "submit.fotolia.com", "username/id", "password"
LocalChDir "C:\new_upload"
RemoteChDir "/"
PutDir "*.jpg"
Disconnect
2. Add those script to scheduler and set the time.
3. Create new_upload folder.
4. Aim your PyroBatchFTP to new_upload folder with script above.
5. Once your file are uploaded, move your images from new_upload folder to another folder.
Usualy I done that process one a week with 30-60 images on 7 agencies, I set the scheduler at 1am-6pm, in the morning I open this page to manage my uploaded file, this page is always open to reduce number of tabs in my browser, but still can open new tabs by right click if I need to.
You can also check the uploading result report by opening logfiles on PyroBatchFTP (click file-show logfiles) to check which file are success or error when uploading process.