Which varnish to choose for a first time job (desk)?
Since you'll be finishing the pieces in the building, lacquer is out.  It stinks to high Heaven and unless you use a pre-catalized lacquer, it is prone to water stains such as condensation from a cold glass of water.
I used to prefer oil based Polyurethane but that can have a strong odor too and that odor can last a while.  For simple, tough, (not fancy) finishes I now prefer a water based Polyurethane such as MINWAX (I know, not supposed to do product recommendations).  It's envrionmentally friendly, easy to clean up brushes, etc. after applying.  It does have some odor, but it usually goes away pretty quick.  It also dries quickly.  It will &quot;raise the grain&quot; a bit on the first coat, so you'll need to sand lightly to knock that back down. Second coat should dry very smooth.  Since this will probably get fairly heavy use I'd go three coats.   No sanding needed between 2nd and 3rd coats unless there are rough spots.
Edit:  Adding that you can use a high quality brush and it will level out pretty well.  Again, don't worry if the first coat ends up a bit rough, that's normal.  Just sand lightly and remove all the dust before 2nd coat.