Dastardly Drum Brakes Sticking

So, my wife's 93 Honda Accord had been sitting for about 6 weeks outside in the driveway (she was busy having a baby and doing new Mom things). Went to drive it for the first time in a while and both the rear brakes were locked up and dragging in the gravel. E-brake wasn't on so I rocked the car back and forth to un stick them, which worked to get her where she was going. 

I pulled the car in the garage later to start on some much needed deferred maintenance in my non existent free time as a new Dad (timing belt ,front brakes etc.), and I pulled the rear drums off to see what's up. Little bit rusty and quite a bit of brake dust accumulation, so I disassemble, wire brush, clean and lube everything (used sil-glyde). Put it back together and adjust till I had the right amount of drag, and move on to the other items on my list at the front of the car. 

Come back a couple of days later to do the timing belt and just out of curiosity I gave the rear drums a shove with my boot as I walked by, and they didn't budge. That's odd I thought, so I tried to spin the drums, but they wouldn't move at all! What the??? Out came the hammer and a few smacks later, had it back to where I adjusted it. Both sides were this way. 

What am I missing here? Are the shoes sticking to the drums somehow? Nothing looks amiss on the assembly.

is it humid where you live?

are the pistons getting stuck in the wheel cylinders?

it's either mechanical (shoes sticking to drum) or hydraulic (wheel cylinders not releasing all the way).

Lot rot from sitting?

Park brake cables sticking?

When you checked them, did you get the sandpaper out to scuff up the drums and shoes? If not, they might just stick again.

Did you check the contact points on the backing plate where the shoes rest? The little pads will get grooves worn in them over time and cause the shoes to get stuck. Get out your roloc sanding disc and smooth out the grooves. If they're really bad you might have to weld them up and smooth them out again.

I usually leave the parking brake off is a vehicle is going to be parked for a long time, just in case this sort of thing happens.

Wheel cylinders leaking? Hydrophilic liquid will expedite rust, soften and swell brake material.  Makes them real grabby, in my experience.

I'd second ShawnG. scuff the friction area (drum and shoes) and get the contact points on the backing plate to clean metal, and put some high-temp chassis grease or sil-glide on. Those should be single servo, so there's not (as) many moving parts. 

Thanks for the replies, pulled the drums back off and didn't see anything out of the ordinary. The shoes don't have much wear to them, they must've been replaced before I bought the car a couple of years ago. I don't see any evidence of the shoes being subjected to brake fluid either. It was just weird that in the two days that passed between cleaning the brakes and rechecking them, that they would bind up like that, sitting in my garage, out of the weather.

is it humid where you live?

are the pistons getting stuck in the wheel cylinders?

Not too humid here in central Ohio this time of year, just got our first snow last night though! The wheel cylinders move in and out freely, and there is no moisture under the rubber dust boots.

Lot rot from sitting?

Park brake cables sticking?

When you checked them, did you get the sandpaper out to scuff up the drums and shoes? If not, they might just stick again.

Did you check the contact points on the backing plate where the shoes rest? 

Lot rot was what I was thinking at first, but I was sure I cleaned all that off before I put it back together. When I first cleaned the backing plates and contact points on the shoes, I was pretty heavy handed with the knotted wire wheel on my 4-1/2" grinder, so they are definitely cleaned of rust! Used it on the drums too, so the drums are kinda smooth now, should I make them rougher? Other than some rust pitting, there are no grooves in the backing plates; they are smooth after hitting with the wire wheel. Parking brake cables are free, everything moves and retracts as it should. The parking brake was not left on while it was sitting for 6 weeks, it hardly gets used at all since our driveway is flat.

I guess I'll hit the drums and shoes with some aggressive sandpaper then. There are no grooves in the drums, but a slight lip that can be felt but not seen at the very edge on the side that mounts to the hub. So there's certainly some wear to them, but not where I'd think they are trashed. I'd like to take a skim cut on the drums versus scuffing them up with sand paper, but finding a shop who still has a brake lathe, and someone skilled enough to use it would be a challenge I think. I guess I could replace them if I have to. I won't be able to get back to it for a couple of days, we'll see if they bind up again or not. Thankfully we have another vehicle for her to drive in the mean time!