Quick Release Rack with Horizontal Dropouts I own a 1980s Panasonic (steel) road bike without eyelets for a rack or fenders, and I'd like to add a rack. The seat stays and chain stays on this bike are a bit thinner than I'd be comfortable to use P-Clamps on (and I'd rather not use them for all of the mounting points of the rack). 

There exist racks which are somewhat designed to alleviate this, such as the Axiom Streamliner line shown below: 



This one mounts to the caliper bridge and can use a quick release on the bottom. However, since my bike has horizontal dropouts, I am not sure if there is anything else I need to be aware of for using a quick release mounted rack. Typically the rack will be loaded with 5-20 kg. The skewer is an old Shimano one, probably the original one which came with the 105 hubs.
It will likely work fine and you wouldn't need additional hardware so long as your skewer has enough extra space to accommodate the extra width of those mount plates and still secure snugly.

As far as what you need to be aware of, I'd be conscious of how often you remove your rear wheel.  If you do so with any frequency, this could be a nightmare.  I have a axle mounted trailer hitch mount that I recently had to deal with whilest changing a flat.  Even without the trailer attached it added a level of complexity I didn't want to deal with while being screamed at by toddler fury and being soaked by rain.  Trying to hold a rack in place and get a skewer through in similar circumstances would have been even more unpleasant.