If you are an investor, you probably know you don't need a "buyers agent", as the sellers agent will do all the paperwork for you. All the buyers agent will do is step in and glean 3% paid by the bank. Since you now know this, you can ask the sellers agent to take 4% (instead of 6%) to make your offer more attractive to the bank, or (what I like to do) give an early Christmass present to a realtor that pulls comps for you and have them submit the paperwork and yell love you for the bonus.
And to answer the question... If you are working with the bank REO, send the SS offer to the REO agent or Realtor and keep up with them each week. If the "owner" is still in the house (pre foreclosure), you have to put together a SS packet (with contract, hardship letters, etc.) and submit to the bank. Let me know if you need help putting a packet together. Good Luck!