(Odd combo, isn't it? Fuller can be pretty trippy, but he seems like more of a speed type of guy.)

For sure it sounds like Park Row was Fuller's personal favorite. It would be nice to get somebody who knew him to confirm that from his own words though. .
close observation or intimate knowledge
Yes and it's a pretty neat trick to convey that, since a stoner can't even remember what happened five seconds ago, so how to recall the experience let alone describe it? I've been there, man, trust me. I know the observation is good, and even the feel of being stoned is well represented in a fresh visual way. Obviously Araki was looking for something light after Mysterious Skin (though his handling of that isn't heavy-handed; and he shows a light touch with heavy stuff throughout his earlier work). Indeed Anna Faris does an excellent job. Unfortunately though I found Smiley Face didn't leave a strong impression and I'm sorry it isn't better or more memorable than it is. Possibly for that reason but also simply due to other circumstances I didn't get to write a review of it. I think if you talk to comic masters (Steve Martin, Seinfeld, for example currently) you find humor doesn't just "happen" naturally. It takes a lot of work. Scenes in Dude, Where's My Car may be "artificial" in that they're self-consciously achieved, but one or two of them are quite memorable and you need to remember something for it to work. I think when you feel a movie "reaches" for laughs it's because the writers have failed. The effort should not show. But the reaching is always there. And all humor is grounded by experience.

There are many movies that depict drug use but only a few even try to convey what it feels and looks like to be high on drugs. One that comes to mind for me is the underappreciated Spun (2002), , directed by Jonas Akerlund and written by Creighton Vero and Will de los Santos, starring Jason Schwartzman and others, which is about methamphetimines, but really gives you the feeling of being stoned.