Moving that many gigs of data across your network could also take a long time simply depending on your network configuration. Before spending a huge amount of energy tuning postgresql, I'd probably look at how long it takes to simply copy 20 or 30 G of data between the two machines.
I have performance issues with two big tables. Those tables are located on an oracle remote database. I'm running the quert : insert into local_postgresql_table select * from oracle_remote_table.
The first table has 45M records and its size is 23G. The import of the data from the oracle remote database is taking 1 hour and 38 minutes. After that I create 13 regular indexes on the table and it takes 10 minutes per table ->2 hours and 10 minutes in total.
The second table has 29M records and its size is 26G. The import of the data from the oracle remote database is taking 2 hours and 30 minutes. The creation of the indexes takes 1 hours and 30 minutes (some are indexes on one column and the creation takes 5 min and some are indexes on multiples column and it takes 11 min.