The big lock forward missed the majority of the 2016/17 season with a shoulder injury but he's back and ready for the challenges that lie ahead.
Speaking to Warriors TV, Greg said: "It's been pretty tough, as you'd expect! I haven't done a full pre-season in a couple of years - I've avoided it due to injury, or swapping teams, or World Cup campaigns, so it's actually been really good to get up and running. I'm loving it."
It's been a summer of transition for the Warriors with a new coaching team taking charge.
Greg said: "You've swapped out both the forwards and backs coaches so of course there'll be some change. Kenny [Murray] is still there so we've got that consistency, and George [Petrakos] has pretty much taken over the strength and conditioning side until Phil Healey gets here.
"All of the coaches have done a really good job - they've stepped up and want to run the systems, and we're all benefiting from that on the field.
"The last pre-season I had was back at the Waratahs, and that was pretty gruelling - it was six days a week for 12 weeks, and it mentally broke me!
"This one has been great though - it's been a balance between the science and the work on the field. We're seeing our results and our bodies constantly improving throughout the process.
"I think George has done an excellent job, and the fruits will come to bear soon. Chico [Francisco Tavares] has also brought in the boxing sessions on Tuesday afternoons, which is different. It beats sitting on a wattbike for 30 minutes, so it's a different stimulus."
The bulk of Glasgow's Scotland players have now returned so pre-season training will move up a notch and the USA international is looking forward to welcoming his team-mates back into the fold.
He said: "Competition breeds excellence. In the second-row, we've got some international stalwarts like Swinno [Tim Swinson] and Jonny [Gray] around, so with myself, Scotty Cummings and Brian [Alain'nuese] there as well it makes everyone perform better.
"There's been that missing element with the international boys away, but the Academy and under-20 boys, as well as the rest of the senior players, have created a really tight-knit group. The under-20s did really well, and they're like little sponges soaking up all the information!"
Attention is turning to the upcoming pre-season fixture with Northampton Saints in Stirling. The match is set to mark Dave Rennie's debut in charge of the Scotstoun side, and Greg is looking forward to the arrival of the Super Rugby-winning head coach.
"It'll be good, because it'll re-affirm everything we've been doing over the past two blocks.
"For him to come in and tell us we're working in the right direction, that's what we want to hear. It's been a bit awkward, having 30 or 40 blokes crowded round Skype with him as the big, ominous face on screen!
"It'll be good to start focusing on game preparation. We've done a minimal amount of that so far, but even just to get out there and throw the ball around for 80 minutes and see how we feel compared to last season will be great."