The Queens Of The Stone Age star has been producing tracks for the Scottish rockers' forthcoming album 'Only Revolutions' and the group admit they were in awe when they first met him.
Drummer Ben Johnston said: "He's an intimidating guy - when he walks in the room he commands respect.
"He is very intimidating - purely by the size of him - and the size of his hands when you shake them. You need two hands to shake one of his.
"He's a big sweetheart and a true rock and roller and I'm sure he could out party just about anyone."
Despite their nerves, the group enjoyed their sessions with Josh and are delighted with the results.
Singer Simon Neil told BBC Newsbeat: "He came down at midnight having tucked his kids into bed and came by the studio, so it was a real big deal.
"What he put on the record was amazing - we love Josh but if it was rubbish it wouldn't have gone on.
"I saw them in 1997 in the Glasgow Cathouse and 12 years later Josh is playing on our records - that's a dream come true for us."