I used to sell a thing called a "Pre-Val sprayer" at auto body stores I worked in ,it was a glass jar with a pressurized power canister you could buy extra canisters for,and pour any paint & thinner or reducer,or anything else you desired into the jar,so you could spray "professional" mixed auto paints at home without needing a spray gun or air compressor..they used to work quite well,not sure if they still exist or not..you'll have a much better chance of matching the paint if you get a factory packaged quart than any spray can touch up stuff for sure..
And I agree--Dupli-Color sucks..their touch up paints are crap,they are usually laquer and they make OEM enamel paints bubble up,and are this as water and run way too easily...their brush on bed liner is the worst too,out of all the different brands--I tried it and several others I know did too,despite anal preperation of the surface,it peeled off after it dried very easily..Herculiner I used worked excellent ..