Winger Reid, sidelined for two and a half months with a serious groin injury, played for almost an hour as Parkinson's side took npower League One promotion-chasers Brentford to extra time in their 4-2 second-round replay defeat.
Striker Hines, who returned as a substitute in Saturday's draw at Southend after a seven-match lay-off due to an ankle injury, made his first start since mid-November.
Reid lasted just under an hour at Brentford, while Hines was replaced in the 67th minute and Parkinson said: "It was certainly a boost to see them both out there.
"We knew we couldn't risk them both for the full 90 minutes so they probably got out of the game as much as they could have. Normally you would have given Kyel and Zav a reserve match each to get their match sharpness back.
"Because of our recent run of games though, we've basically had to give them their run-out in an FA Cup match. They will certainly benefit from this and be an added bonus to us once the games come round in the next few weeks."
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