Harm stilled when Luke groaned, cocking an eyebrow at him even though he wasn't visible at the soldier's back. He was trying to decipher whether the noise was a good one or a bad one - momentarily distracted away from thoughts of the arm, even though it was being described - when he got confirmation that what he was doing felt good. He beamed, filled with a gush of pride that he could affect Luke so. He pulled a silly face in celebration of his victory before he cleared his throat and leant forward.
"If you take your shirt off, it'll feel better," he hinted. Luke's hands obediently returned to his buttons - there might have been a moment of hesitation, Harm wasn't certain - and Harm helped him out by tugging the tail of his shirt free of his chinos and taking the pink garment by the collar when it was finally free of Luke's body. The glove was left on the mattress in the process, he noticed, which pleased him. He got off the bed, scooping up his discarded jacket on the way and laying both of items of clothing on a nearby chair back, so they didn't get crushed.
As he padded back to the bed, he admired Luke's exceptional physique from behind, reminded of Emma Stone telling Ryan Gosling (as she gasped at his ridiculously-gorgeous body) in that movie, "It's like you're Photoshopped!" Luke definitely appeared too good to be true and yet, here Harm was, crawling back onto the bed behind him and getting to put his hands on him. It was a surreal moment, one Young Harm would've absolutely died to have happen, yet it had come about with no excessive machinations whatsoever. An organic moment was so much sweeter for the authenticity of it, he felt. Harm was grateful to the universe for helping him be patient enough to earn this moment.
Although there was still much to be said about the arm, many things he wanted to ask and poke at, Harm was content to massage silently for a while. Now that he had unfettered access, he was able to use his whole hands to prime Luke's muscles for his attentions by squeezing and pinching gently up his neck, along his shoulders, down his arms to his elbows (it was interesting, the different sensations of the two arms in each of his hands simultaneously) and down the undulating plains of his back - as far as the top of his pants, anyway. Once that was done, Harm repeated the same routine, this time with gentle fingertips and his thumbs, attempting to stimulate blood flow into the areas he'd soon be pushing around, with the intention of assisting healing in the muscles as he abused them.
Not that Luke was in any danger of needing it. His muscles were more likely to resist Harm's ministrations than suffer for them, but he had a way he liked to do this and it had worked for him with other people (mostly men, admittedly), so he could just hope it brought some benefit to Luke.
Finally ready to really dig in, Harm began massaging Luke in earnest. He quickly worked up a sweat, using his thumbs and the heels of his hands to manipulate the intense, knotted muscles of Luke's traps. He glanced around after ten minutes, wondering what the thermostat was set on - it was hard work and his brow was dripping sweat into his eyes, his cheeks flushed with exertion - but not seeing anything close by. Without missing a beat, he grabbed his own shirt and pulled it off, dropping it negligently on the floor behind him (after using it to wipe his face dry). That was better.
Harm's routine continued for close to an hour before he began to tire. He would start with intense digging, prodding and poking, pushing tension sideways and away from where it was knotted, then massage the whole body gently to disperse the energy. After that, he would chop with loose fingers (so that they smacked together to deliver a bit more pressure) or dance with fingertips before resuming prodding and squeezing in a new area. Luke's shoulders were attended to first, then his neck, followed by his back and then his arms. Pressing thumbs into triceps was usually very relieving; biceps were more difficult to manipulate and Luke's were no different. Harm massaged his left arm first, then attended to his right, finding it unusual to mould his hands to. It had been silent long enough - apart from Luke's breathing and Harm occasionally checking if pressure was too great or too minimal - that he thought it was time to return to his ponderings about the appendage.
"So, this arm can take on any shape, huh?" he smirked as he ran his cupped hands along it all the way to Luke's fingertips before massaging his way back to the shoulder. He did his best not to press his bare front to Luke's back - he was misted with sweat and it would be unpleasant - but the angle meant he leant against him (as he had every other time he'd massaged his arms). "Beats me why you'd ever need anybody, in that case, when you have an arm that can transform into anything," he giggled. It might be childish but if he had an arm that could shift shape, there was no way he wasn't turning it into a different sex toy every night.