In the stifling conditions, Rainey estimated she lost 2-3kg per game - the team management would test them after every match to get their personal water intake correct and make up for the lost fluids.
"I got lots of game time because I was playing midfield. There was three of us and we would rotate these two positions - three-minute rotations.
"Six minutes on, three off. Go off, get your breath, and a drink. It went very fast when you go off."
Rainey rated her personal highlights as being against Australia - one hard shot she made deflected slightly off a team-mate for a goal, and she also made an excellent dive tackle in the shooting circle to prevent an Aussie forward taking a shot.
"The level of hockey is just so fast," Rainey said. "It was really fun and amazing to play at that level."
The Japanese team gave the toughest test, although this was helped by them requesting to play each match in 17-minute quarters, rather than the 35-minute halves of the Anzac clashes.
"They like to play in quarters. We prefer the halves. The first quarter they were all over us, we had no possession.
"Had to get back into it in the second quarter and scored a couple of goals."
Rainey will receive a written report from her coaches next week, which could cover areas of praise or specific things she needs to improve.
"[I'm expecting] a bit of both - there's always something to work on, hopefully I did something right over there."
Rainey will also train in Palmerston North, and has a development camp coming up in Tauranga.
Her first national call-up came after a dream season where she was named player of the year by the Wanganui Hockey Association, most valuable player for her Wanganui High School team, best attacker by the Collegians club and the most improved female for the Central Districts association.