Honestly, your friend's response frustrates me. Being autistic and having difficulty understanding social situations is not just some excuse, it's literally part of being autistic. Sure, work on it all you want, but if you're autistic there will never be a point in your life where you can intuitively know a person is feeling some type of way. You might be able to tell something is different, but knowing what is actually going on is much more difficult (it's difficult for everyone, but so much worse for autistic people)

Your friend might as well be telling you to learn how to fly. The best you can do is notice there is some change in their behavior and ask what's up. There are some obvious indicators like crying, but even that can be an expression of various emotions. You can try to understand the context, but most likely the things you think are important aren't even relevant.

The real solution here is when your friend needs more support, they should ask for it. They shouldn't lash out at you after the fact, they should ask. If they can't do that because their autism gets in the way, then they should understand that you also have trouble recognizing their distress if they can't even express it clearly.

My teeny bit of advice:

Step 1. If you think there’s any possibility someone’s not feeling well just ask (2 hour minimum interval)

Step 2. If they say they’re fine/ok, take them at face value. If they’re not ok see how you can help.

I find most people (read: mature adults) will appreciate the check in and will understand at a minimum that autism makes it hard to read people well. My experience with autism is definitely that I will shrug off social indicators as “not concrete enough” but just asking people how they’re doing even if you’re often wrong is a clear way of showing that you do care even if your emotional barometer sucks.

sometimes people want solutions and sometimes people want "damn that's rough anything i can do to help" asking them this straight up helps me a lot.

things that can help include but are not limited to:

thing to help take mind off thing

help them rant to release pressure

go out for a little treat

"sorry to hear that pal, that's fucked" or similar

check in with them later (this is a big one honestly, people don't expect it these days and does very much show you care)

I don’t have a resource, but you’re not alone in this - I struggle with this too (usually while walking away and going through my mental conversation checklist realizing that I’ve forgotten to ask people about themselves…). I do genuinely care, I just want most social interactions to be over asap and have about a dozen dvd logos bouncing around the corners of my brain lol.

I echo what others have said though. For me it’s like any physical exercise, repetition and training are key. And learning my own boundaries around mental/sensory overwhelm; because if I’m overwhelmed but ask out of obligation and then someone starts talking about their issues, there’s a non-zero chance I’ll immediately glaze over.

I solve this the autistic way and just ask people how they want me to support them. It may not be romantic where I automatically know what they need and do it without them telling me, but it can't be wrong if I'm reliant on how they tell me they like to be supported.

I think the book I read that helped me understand communicating was "Feeling good together" by David Burns. I did a lot of the techniques given to make me a better communicator and listener

Have you read unmasking autism? I think it's a great resource for you to feel more comfortable and to also recognize the outward signs of stuff not going great for other ND people around you.

Also, it never hurts to ask. My flavor of neurospicy is one that really needs verbal confirmation of things. Sometimes it's awkward when you ask someone "hey, just making sure you're doing OK", because they're indeed OK and now are wondering why you asked. But when I'm not OK and one of my friends checks in on me because they noticed me drifting off in thought or something, it gives me the chance to externalize what's making me feel bad.

Hell, sometimes I didn't even notice I was sensory or emotionally overwhelmed til a friend checked in on me and made me realize that I was not feeling great, and that I could do something about it. So, my advice is to just straight up ask. Talk to your friends about if they would like to be asked and how, but yeah, blunt, clear communication might not be as exciting as other ways of noticing you're not doing so hot, but it's effective.

Not a resource per se. But when I was younger, therapists were kinda frowned upon and a common joke in the zytgeist would be that in the midst of you having a breakdown they'd ask, "so how does that make you feel." So as a kid I just started saying that as a joke which put me in some very awkward situations as people would actually tell me how they felt! Because of this, people tend to think I'm a good listener. And I am, but it wasn't on purpose.