"It was a bit of a shock to the system, but it was just a case for the boys of shaking yourself off, putting a smile on your face and getting on with it," said Rees, who arrived back in Cardiff with the squad yesterday afternoon.
"The sun had just about come up, the squad had time to grab a shake and warm-up and then went into a full on rugby session which was up and running at full tilt by 5.15am, before then going for breakfast.
"The whole camp has been about mental and physical toughness, so I thought the coaches had got it spot on. It's certainly not something we are used to, everyone was physically fatigued and taken out of their comfort zone a little bit more.
"It put everyone under pressure at the end at the end of a long and hard week it was the last thing anyone wanted to do, but that's exactly the kind of pressure we will be under at the World Cup.
"The pressure will be on and we will have to perform, but it all starts with England next week. We've put the hard graft in and, from now on, it's all about the rugby."
The Wales squad now have a couple of rest days ahead of them before meeting at the WRU National Centre of Excellence at the Vale Resort, Hensol on Monday.
But Rees and his fellow players have invited fans into the Millennium Stadium next Tuesday (gates open at 2.30pm) to watch them train for free and the Scarlets captain says he is particularly looking forward to the 'homecoming' session after the isolation of training in Poland. (logon to www.wru.co.uk/watchwales4free to register and for details)
"It will be good to train in front of the fans and we are all looking forward to a run-out back home at the Millennium Stadium," said Rees.
"We had a few thousand watching last time we opened the stadium doors in this way and it makes the atmosphere in there more like match-day and gives the boys an added lift.
"It will be a sharp contrast from the isolation and intensity of Poland, but great to be back in our own backyard in front of our own supporters."
Wales have back to back fixtures against England starting at Twickenham next week and then returning to the Millennium Stadium on Saturday 13th August.
With the Twickenham fixture an apparent sell-out and more than 52,000 sold for the return leg in Cardiff, Wales can look forward to a good send off from fans for their final warm-up game at home to Argentina on Saturday 20th August (with tickets for that game on a 'buy one get one free' promotion).
Rees is adamant that his side must repay the faith shown in them by fans that have already put their hands in their pockets and bought tickets to show their support this summer.
"The biggest thing for us now is to make sure that we go into the world cup full of confidence and self belief because we have performed on the rugby field," said Rees.
"We owe it to the fans and we owe it to ourselves after all the hard work we have put in over the last few weeks. We have two fixtures now against England and a final match on home soil against Argentina where we need to go out and play.
"This is a talented and dedicated bunch of lads and we enjoy our rugby and, hopefully, that will show out on the pitch.
"We know South Africa's strengths, but we have ability and guile throughout this squad and we need to go into that first game brimming with confidence based on these August warm-up fixtures.
"Warren and the coaches need to pick their final 30 before New Zealand and I know the boys have made it difficult for them. There have been no egos, no one relying on reputation and the competition right across the squad has been intense.
"The younger players have pushed hard, but the senior boys have made sure they have put their hands up to and everyone to a man has done what has been asked of them.
"We are a stronger unit for it and should take confidence, but now we must perform."
Tickets to the Wales vs. England Rugby World Cup warm-up match at the Millennium Stadium on Saturday 13 August (kick off 2.30pm) are priced £30 and tickets to the Wales vs. Argentina on Saturday 20 August (kick of 2.30pm) are priced at £25 and are on a 'buy one get one free' promotion.
Fans can also purchase their tickets for the Millennium Stadium clashes offer online at www.wru.co.uk/tickets or by calling the ticket hotlines 08442 777 888 or 02920 230130 or at local Tesco stores
To attend Wales' open free-to-enter training session at the Millennium Stadium next Tuesday 2nd August (gates open at 2.30pm) logon to www.wru.co.uk/watchwales4free to register and for further details.