Getting sexual gratification is pretty easy these days. Achieving intimacy - not so.
Achieving intimacy requires an investment in time, energy and emotions, to mention the few.
Besides the obvious things as lots of body contact, to which, I guess, most guys subscribe when thinking about m2m intimacy, knowing the other guy, his likes and dislikes, and showing that you care adds up to the feeling of intimacy.
A str8 friend who is a good chef conspired with couple of my gay friends and they threw in a nice home-cooked meal for me, after I returned from a grueling business trip. This took some time and trouble, and since they cooked up a pretty fancy dinner, much to my personal liking, I felt that this was an expression of intimacy.
Few dudes I am friends with tend to exchange clothes with me, and wear my clothes because they are going to a party, and want to score
and I wear theirs admittedly for the same purpose. Actually, we are just exchanging acts of intimacy.
Years ago, when most of the world smoked, my Dutch friends would always light a cigarette and passed it on to me, and I would do the same for them. This used to be some sort of kissing the other guy without actually doing so.
A dude, I am friends with enjoys stealing food from my plate. There is no shortage of food where we live, hence, there is no need for stealing the food from other dude's plate, but I see this as a subtle expression of intimacy.
Some of the college friends of mine str8 and gay alike used to express their sense of intimacy by using the bathroom together. Actually, no one thought of locking the bathroom door if your buddies were in the house with you. A dude was showering, taking a dump, shaving or even jerking off. Another dude bumped in, cracked a joke, and sometimes fooled around, and sometimes just 'reported' him to the rest of us, who always agreed that the dude was 'disgusting' just as much as we were, too.