Set up the fast poster time out to 90 seconds. Make sure the list is random so not to overload the servers with multiple posts.
Update your "Slow and Manual Poster Blog Links" settings found in the settings menu. Max it out to 4096 KB. It is not documented but the Fast Poster also uses this setting.
To randomize the list, load it into harvester, select the blog analyzer add on, load the list from harvester into the analyzer, select shuffle, then save the list...