I've used the Chroma Clear and the tamiya ts13 also.
Many internet sources sell it..shipping can be an issue though.
I have a good friend who paints 1:1...its his Chroma Clear leftovers I get and it is mixed per the instructions...I shoot at 22 to 25psi
I noticed that your from Maine...the total opposite of where I live.
As a result the info I would give you would be next to useless as the environment is totally different.
But I would say in your area (cold weather / heaters ) the fumes are quite nasty and toxic and much more dangerous than lacquers.
I assume you are using a respirator already.. .if not GET ONE NOW!!!!!!!.If you are venting your booth outdoors the fumes for others
will dissipate. if your shooting in the basement....do not use the urethanes......I shoot a lot of the HOK colors that are urethane...but do not add hardener, just clear it with lacquer, as we are talking models.
The results that urethane clears give you are quick and easy.......but think safety first.