Old Dick, I posted over on LFInfo last year, or the year before, a "varnish" used by Strand, as passed to me decades ago by his closest friend, photographer Walter Rosenblum. I print on Ilford Warmtone semi-matte, using the glossy only for proofing the negs. The glossy surface has been made glossier than it was years ago, more like patent leather. The following is easy, though some will question its effect, like that of wax, on the print. It will not produce the gloss of air-dried glossy paper, but it will provide a soft luster and bring back the print scale and detail in the low values.
If you are planning dry mounting, do that first. I currently dry-mount my print on 1-ply stock for flatness and hinge-mount that to the mount board which gets a window over-matte.
Mix some artist's stand oil (a refined type of linseed oil) with some high-quality artist's turpentine (I use Windsor-Newton) in a ratio of about 1:4 in a 4-ounce glass bottle with a tightly fitting cap. You'll want to work in a room with good ventilation. Shake well, add a small amount to a cotton ball, and spread over the print in overlapping small circular motion, adding a bit to the ball if needed. When the print surface has been covered entirely (perhaps 30 seconds for an 11x14), immediately use fresh cotton balls to wipe the residue off, turning to keep a fresh surface to absorb thw residue checking carefully to make sure the varnish has been equally "polished". A minuscule layer of oil will be absorbed by the emulsion. Let dry a day or two before framing or storing.