I have tried a few methods.
Instead of a table saw, I have used a tile cutting saw. It's a small table saw that has a reservoir for water. And it uses a diamond blade. Ignoring the other pitfalls of my cheap tile saw, the obvious suck is the wide kerf, the noise, and the water spray. Oh.. also the hand-numbing vibrations.
I have tried using a bandsaw, but FR-4 is too abrasive for steel blades. It's not worth the time of changing out the blades, let alone the cost. I cut approximately 2 feet of 0.064" FR-4 before my 100" long 6TPI blade stopped cutting and started burning the FR-4. Boy, it threw some sparks. Carbide blades might work out, but you need an 18" bandsaw (for maybe $2K) to even fit a carbide blade. And carbide bandsaw blades cost like $250.00, themselves. I have neither.
So then I built a small router table which holds a Proxxon tool (15k rpm Dremel sized rotary tool with very low runout and very low noise). I have toyed with the V groove pointed carbide cutting bits, and they won't work in this setup because the spindle speed (and/or rigidity of my table) isn't high enough. They cut herky-jerky and quickly dull. So I added a tilting mechanism so the rotary tool can tilt 45 degrees. Using a square carbide endmill tilted 45 degrees, it cuts a 90 degree V groove in FR-4 like no tomorrow. To me a tad more precise, perhaps at a feed rate of a couple inches per second with groove depth of about 0.8mm. With just an adjustable fence, it's all you need to cut straight lines. I can score a 0.032" thick FR-4 partway through so I can depanelize it by snapping it, later. Or I can chew through 0.064" FR-4 in one go, if I want; generally, I would cut halfway through and repeat on the other side, though... to keep the kerf smaller and to reduce the dust. And if you want to clean up the edges, a router table guarantees a parallel edge. Just flatten one edge on the disc sander, then route the opposite edge on the router table (with the endmill straight, of course). This is relatively low dust, because all the dust falls straight down, into the table. I don't use it with vacuum. I just sweep the dust with a brush. I feel like that's better than the vacuum possibly blowing fine particles into the air. I have cut a good bit of PCB's with it, as well as wood, plastic, and steel. I use the same endmill for 95% of whatever I cut, and I still haven't worn out the first bit.
I'm not sure if all the small to medium sized wood / plastic / aluminium working mills can even generate the right spindle speeds and have the right kinds of tool capabilities to work at the RPMs needed to cut FR4 in 1-2mm diameter slots
1-2mm slots? Probably not at any reasonable feed rate. I can cut perfectly straight slots in FR-4 with an 1/8" endmill. Or even with a slightly smaller carbide drill bit. But the slot has to be slightly larger than the bit, so I can make a clean finishing pass in either direction. And I need to have a reference edge that is parallel to the slot. As aforementioned, the max RPM on my Proxxon is only 15K. Most Dremel tools go up to 25 or 30K. With my setup, this is nominally 3mm thick at the minimum, and this is quite a bit slower than the turbo-tilted-V-groove. 2mm sounds unlikely with a standard rotary tool and a straight endmill. But do the math on a 90 degree V groove going say 1/3 the way through the thickness of your board on either side, what does that come out to? About 2/3rds the thickness of the board, methinks. Winner, winner.
Edit: as for cheap guillotines, I find they will work on FR-4 max thickness of 0.032" which I think it 0.8mm? The cut tends to veer away from the cut line, and the board tends to be left curled, a bit. Better on 0.020 and thinner, IMO. If you wanted to cut thicker board, and the curl (internal fracturing) damage isn't an issue, I would think aviation tin snips would do the job.