Here's how I use to do it:
I would just walk up to the runway, get in the plane and go for a 2ish hour flight just because with nothing more than a glance at the weather and a preflight. When I rented or borrowed a plane, it was the same way. No phone calls to FSS. No computers. Just get in the plane and go. At nearly every airport I would go on a walk and snoop at planes on the ramp and in open hangars. There were few if any fences and the few fences had open gates or were unlocked. Lots of airplanes were unlocked especially if they were being used at the time. Security was hi I'm ___ how are you beautiful/crappy day for flying isn't it. I never locked the plane if I were staying at an airport and sometimes even when going into town for lunch. We personally left the plane unlocked in the open hangar on the farm with the key sitting on top of the glareshield 24/7/365 and there were no locks on anything and no fences.
Many times we would get up in the morning, looked outside at the beautiful early morning weather, sometimes but not often made a quick call to FSS for a general WX breifing if we had questions, and said let's go on a trip and we were gone. I don't ever recall asking for flight restriction areas because they were clearly marked on the sectionals. I think my aunt asked them about one for the 1976 NY parade of ships but I recall sitting in the backseat looking down on the huge masted ships later that day.
Here's one super excellent trip that took all day: Get up and look outside at the good wx. Preflight planning was on the breakfast table with a butter knife for navigation and to determine fuel range. Walk up to the runway and lift off moments after sunrise with dew rolling off the wings as the plane accelerated. Our FSS equivalent briefing was nothing more than the view out the window at 3500 or 4500ft without using the radio. Weather good = keep going. The only weather reports we got was talking to other pilots or ramp rats at fuel stops. We popped off a pirep or two just for fun to FSS. The route was this: Upstate NY to the Hudson River then to Long Island and over the city. Straight through the triple NYC TCA at 3500 or whatever ATC told us to maintain. On to Montauk airport. North to the mainland somewhere just east of New London. Follow the coastline around to Rhode Island Sound (Buzzards Bay maybe?) then continue across to Martha's Vineyard and Nantucket. From there, across to Cape Cod, over Boston to Plum Island. West to Springfield Conn then sort of direct back to the farm in Upstate NY. Avoid the rare R- circle on the charts, contact towers as needed to get in and out and all was good.
Consider the hassles of making that flight tomorrow morning without calling FSS or getting any kind of notam breifing at all. It was no big deal routine run of the mill flying then. Today I'd guess you'd be risking gitmo or at least a serious spanking by the FSDO if you did it exactly how we did it then. The dreaded ADIZ was some offshore or national boundary thing that was a total non issue and even then it was a non event when the line needed to be crossed. No double secret ultraviolet secret passwords were needed.
On roadtrips with ground vehicles I pull into airport parking lots around 7-10pm and overnight without telling anyone then leave in the morning. I would often just walk out onto the ramps and drool on airplanes or sit in the grass between the taxiway and runway and watch planes takeoff and land if I got there early enough or in the mornings. I still do that in general however since 2001, I've gotten the hairy eyeball numerous times and I've been questioned twice about who what when where why - once was by the local sheriff. Nowadays if the FBO is open, I always make sure I go in as soon as I get things shut down. At laid back podunk airports it's still no big deal however if there's a city nearby, ish, I'll just drive by and keep going.
I've been around airplanes for 40+ years and today I'm intimidated by some GA airports. The one near my parents house that I use to fly from regularly was really scary about 3 years ago. That relaxed little airport has turned into something that makes the low security prison and state patrol facilities 3 miles from where I am right now look like nothing. The airport looks like this: Really tall fences, razor wire on top. Locked gates. More warning signs than I've ever seen in my life. The fairly small parking lot is surrounded by very intimidating fences on all sides except the entry road. The place was absolutely devoid of human life like an abandoned city would be. There wa a learn to fly here sign however the place was so gustappo that I turned around and left. Besides, I wasn't sure how to go in to chat with them or to talk about going flying since the gate to the FBO was locked. BTW, that was a saturday afternoon where in the old day it would have dozens of people all over the place and airplanes moving all over the place. I really hope other airports are not like that.