McDermott's men guaranteed automatic promotion on Tuesday night with a 1-0 victory over Nottingham Forest in front of 20,000-plus delirious fans.
But it was a far cry from the way Royals last went up to the Premier League under Steve Coppell in 2006 when McDermott was the club's chief scout.
The 51-year-old explained: "When we got promoted in 2006 I was scouting a game at Brighton. I was sitting in a motorway layby thinking how great it was to be promoted. But I was on my own because everyone else was at Leicester City.
"I'm manager now so this time it is completely different. I've been in this job two-and-a-half years and I've got a promotion under my belt and a lot of managers haven't done that."
While Reading's promotion in 2006 was secured at Leicester City, Tuesday's occurred in front of their own supporters who invaded the pitch at the final whistle and stayed behind for an hour to honour McDermott's team.
The champagne corks popped long into the night before McDermott and his staff hit popular Reading town centre venue the Purple Turtle where the party went on for a few hours more.
And McDermott revealed that a conversation with Coppell the day before Tuesday night's match prepared him for what was to come.
"I spoke to Steve Coppell about this," he said. "I asked him how long you are happy for and he said about 20 minutes. I think it's more like five minutes with me, but he said I would have a glow at the end of the season if we achieved something, and I guess we have."
McDermott has received hundreds of messages of congratulations since Mikele Leigertwood's 81st minute winner sent Royals up.
Promotion is believed to be worth around £100 million to the club and McDermott added: "We're in the Premier League now, we've been promoted and I can celebrate for the next couple of months.
"We were nervous on the night and there are 100 million reasons for that. We weren't as fluent as we can be, but maybe we can excuse ourselves for once."