While most of what you said makes sense how do you find someone at the companies you're interested to talk to? I feel like unsolicited linkedin messages to developers at the company could backfire.
The only "trick" is to find the balance between pestering strangers and showing a genuine interest in the experiences of the people you talk to.
> Hi you have a $COMPANY shirt on, can you get me a job
would likely come off the wrong way whereas
> Hey $NAME, you work at $COMPANY? I've been thinking about applying there and was curious if you could tell me what you think of it?
Would likely get them to talk to you, and if things are going well, they'd likely introduce you to someone or offer to pass your contact information along.