Humbrol is good. I never liked enamels for the kind of painting I do. It does take some getting used to. Do thin layers if you want it smooth, thick can go wrinkly, but that might be a desired effect.
It is touch dry in 1 or two hours but leave it a day for it to cure propperly.
You have 3 grades of enamel paint:
waterbased, oil based and automotive.
All enamels share one characteristic ... a hard surface from the result of a crystaline structure.
Model paint enamels are oil based ... just formulated to be usable with a 00 brush not so much sprayed or painted with a 4" house brush. for big spots, use regular oil based enamels, small details ... model paint. ... spray paint is also an oil based enamel, just formulated to be sprayable and dry fast.
waterbased enamels have the effect of enamels, but with a shorter drying time and easier cleanup. not as durable ... but so much easier to use.
automotive enamels are true enamels ... they can me baked to a solid layer or left for 2 weeks will form their crystaline structure on their own as the oils dry out. they can be painted onto with other oil enamels, then clear coated with an automotive enamel which will provide protection of the work.
drying times vary ... make sure you also find out the CURE time (i.e. spray paint has a dry time of 15 minutes, but the cure time is anywhere from 24 hours to 7 days depending on brand and thickness)
In-grid,i left a comment on your question somewhere concerning enamal paint which i do use to highlighten my colours on a hard surface like fibrite. I do buy it in our local artsupply shop ,small bottles of the brandname Pébéo which are quite expensive,around 4E for 2o ml,i think,and i do use it on top of acrylic paint at the very end, drying time about 1O minutes,yellow is my favourite colour as it does change a blue into green,a red into orange and it does give a nice shine to a brown,ocre and yellow.You can also paint directly on paper,it's transparent and very glossy,depending what you do, it's an interesting medium to try out!Once i bought a whole lot on internet from a German supplier, way cheaper than the french ones,it came to 1E the bottle but you have to hunt around for it!