Probably would be a good idea to flush the entire system... so do the steering rack as well - which will involve doing lock-to-lock steering (front end lifted off the ground) quite a few times. Even though both are hydraulic fluids the additives are different and brake fluid has the potential to damage the seals on the power steering system over a long period of exposure.
2011 F-350SD - SRW XLT FX4 CCLB: 6.7L PSD, 6R140, 3.55:1 EL, Job 2 (Daily Driver)
With BDS 6" 4-Link & Rear Leafs, Fox 2.0 IFP, Toyo MT 38x13.50R18 on 18x9 Fuel D525, Bulletproof Prerunner Bumper, EGR/DPF/SCR delete.
1994 RAM 2500 - SLT Laramie 4x4 RCLB 5.9L 6BT NV4500 (Project)
2009 Tundra - SR5 4x2 RCLB 5.7L 4.30:1 (Sold)
Others: 1995 F-350HD DRW 4x2 CCFB 7.3L-T444E PSD // 2004 F-350SD SRW 4x4 CCLB 6.0L-VT365 PSD.