A few points I'd like to hit on-
DO NOT try to cut corner or cheaop out when it comes to safety equipment!!!! There are a lot of ex-painters who thought that these chemicals weren't "all that bad", and now can't walk into a room with new carpet without triggering an asthma attack, much less spray any paints. An OV-rated respirator will work, but the filters need to be changed often, which adds up quickly. A supplied-air mask is the best, safest way to go. If you can afford one, get one. If you can't afford it right now, make it a priority.
Also, the isocyanates and other wonderful petro-chemicals are also absorbed through skin, mucus membranes, and eyes. Wear nitrile (NOT latex) gloves, cover up as much skin as possible (full paint-suits can be bought for less than $20, and re-used. A wise investment, imo). Also, wear some safety goggles or something to keep the over-spray away from your eyes. Prescription glasses typically aren't enough, and besides, they tend to get trashed pretty quickly in a spray environment.
Most definitely DO NOT overlook the importance of ventilation. With enough ventilation, using proper fans, spraying 2k clears is really relatively safe. Without it, it's begging for trouble, and lots of it. Ideally, you want an enclosed area with filtered incoming air, an approved non-sparking fan with enough power, and paint arrestors to filter the exhaust (which will save a lot of headaches with pissed off neighbors, too). The non-sparking/explosion proof fan is important. Expensive, but important. The fumes, particulate, and overspray are all flammable. A normal fan, with the electric motor mounted directly to the blades, will pull all of that flammable stuff directly over the electric motor, which creates a spark with every rotation. Condensed fumes+particulates+spark is NOT a good idea.
No, it won't result in you blowing up your garage every time. And yes, lots of people have used those types of fans and not blown themselves up. But, it's the point that it's setting up a potentially dangerous situation. There is a reason OSHA and NIOSH require spray booths to have explosion-proof fans with non-sparking blades, and it's not because the inspectors enjoy climbing though exhaust walls to inspect them.
One last note on the spray-area bit- the requirement for air movement for a legal spray booth is 100 feet/minute of air "across the face of the booth". Realistically, if you can get 60 ft/min to 80 ft/min, you're fine. There are equations you can use to figure out the theoretical flow rates given your "booth" size, fan CFM, etc. I just bought a little wind-meter thingy off Amazon for $30 and use that to verify the ft/min in my booth. Then again, I'm not what you'd call a good mather.
.
As far as good clears, there are a TON of options. My "standard" clear is Matrix MS-42. For me, it tends to resist runs and sags, lays out well, gives a good finish, and is pretty durable. With other clears, I tend to run into the problem of putting runs and sags in the clear, which, of course, leads to more work getting rid of them, lots of sanding, etc. The MS-42 just seems to agree with my painting style.
ALWAYS read and re-read the tech sheet, no matter what clear you use. With most clears, if you want a show-finish, you'll spray 2-3 coats, let it cure (typically overnight), wet sand everything completely flat, then spray another 2-3 coats. I usually let the peice "gas out" for about 24 hours after sanding and before spraying the next round. While sanding, and for a while afterwards, you'll notice the smell of the clear off-gassing.
If you've managed to lay the clear down without any runs, sags, orangle peel, or other defects, call it done. If there are imperfections (which there almost always are), you'll have to color sand and polish the clear, which is a whole other thread in itself.
Sorry if I got a little long-winded there, but, as mentioned, clear coating is a whole artform in itself, and there is a lot of info you really need to be aware of before you start playing with it. Also, common sense is a must. I remember one idiot trying clear coat motorcycle parts in the bathroom of his apartment. That he shared with his girlfriend AND children. He wound up giving himself iso-poisoning and being hospitalised, and ending his short-lived painting career. Hopefully, the rest of his household managed to avoid of negative effects from contact with the chemicals...