Get in touch with someone who can put you very close to the interbank Forex market, such as Currenex or Hotspot FX. You want direct access, where spreads aren't being touched by your brokerage. Now negotiate a commission structure where the fees you pay, plus the spreads you're seeing, are less than the value of 2 pips for the size you're trading. Be aware that you'll need a hefty account size to open with either of these brokers, but Currenex is the less stringent of the two.
Now use only limit orders to eliminate any potential slippage. You're set!