Thanks everybody for your advice! And encouraging stories to continue
Well, it was ~8 hours of cleaning...
Few notes, maybe those will help coming generations of electronics enthusiasts blowing up electrolytics
* Identify what is contaminated. Not just area, all the space, because the electrolyte mist made snow cloud going everywhere including up and then settled. Mine is marked in the picture, see
gallery. Red cross is approximate epicentre where caps were. Yellow - cloud of mist. Orange - splash zone. Blue - whole space cleaned (it extends to the left almost to the other end of the display). Not just that but before, cleaning process and after pics.
* First thought is to save everything, but cleaning is really tedious. Consider what is below the value of your time spent.
* There are two types of damage: splashes and snow.
* Splashes are evil, those need mechanical cleaning first. I used old credit card. Be careful. An experience of mine as an example. I was afraid to mechanically clean the splashes off my beautiful Apple display. Using soapy water or screen cleaner took forever, so I did some mechanical cleaning at the end. Soapy water and screen cleaner for the finish.
* Snow is more or less easy except if in the places like open electronics PCB's, heatsinks and BNC, USB etc connectors. Sponge or cloth, soapy water, paper towels, PCB/contact cleaner.
* Compressed air and compressor are good tools. Especially for blowing out moisture left from water or any other liquids. It can not blow away the snow.
* I'm pretty sure I did not get all of it off.
It seem ok now. I still have to clean the open electronic load. Need to disassemble it. And the transformer. For the transformer I'm thinking that replacing outer layer of isolation might be easier and safer.
Two sub-stories of my adventure.
I was trying to test transformer 2x30V + rectifier bridge + 2 capacitors 10000uF 50V in a dual rail config. It did seem fine without load. It did seem fine with big resistor as a load over both(~0.5A). For short periods of time, less than a minute. I did not check temperature of the capacitors, just the load. Then I connected step down voltage regulator to the positive rail. I have been using that regulator for couple years as a power supply, you can see it in the shelf. I was going to attach electronic load and apply minimal load, but the capacitor of the negative rail popped. I think it was before I managed to connect the load, maybe in the process, but I'm not sure, adrenaline. I have read the theory of linear power supplies and did calculations several times before I did this. But I'm in not 100% sure about what I did. One of my guesses is to blame cheap caps I use for experiments. The other is that voltage rating must be calculated with more redundancy. Third is misbalance, even with minimal unbalanced load (it was ~50mA with step down regulator attached) on just one of the rails of the dual rail.
In parallel I was setting up mini-ITX Windows computer for use with scope and other instruments. I was trying to do it in the virtual machine on my Mac, but that does not seem to work well, some features at all. The computer enclosure was still open and it was running. Fortunately it sat behind the scope, no splashes. But it got some of the alkaline snow. I inspected it very carefully, there was not much snow in it. I removed "snowflakes" with tweezers, cleaned with PCB cleaner, used compressor on it for several times. Working condition, but let's see.
I'm going to continue after more reading. And build the box of plexiglass or something.