The West Yorkshire club face favourites St Helens at Wembley on July 17 after Saturday’s stunning 35-20 semi-final victory over in-form Warrington Wolves.
Tigers made the 2014 final in Powell’s first full season in charge but were beaten by Leeds Rhinos.
Since then, they finished top for the first time in their history in 2017 when they also played in a maiden Grand Final.
The last of Castleford’s four Challenge Cup wins came in 1986 but they must defeat back-to-back Super League champions Saints to add a fifth.
Powell said: “We’ve probably got more experience in bigger games now. It’s against a pretty formidable opponent obviously but we only had two weeks to prepare for that final [in 2014].
“We’ve a little more time here. I do think we’re better equipped and we look forward to it. We know how good St Helens are but we need to go there full of confidence.”
Castleford had lost 60-6 at home to Leeds and suffered three straight defeats before delivering a towering display against Warrington. Powell said: “We had three different meetings this week when we spoke about different reasons why we wanted to get to Wembley. They were great meetings and they raised emotions in the camp and really fuelled desire for the game.
“I knew the boys would play well. We could feel it all week.”
Powell – who leaves to join Warrington for next season – hit back at critics who questioned him after their recent loss of form. He said: “We showed what we’re about and we still care.”