That seem to be the way to go: working it in to the top of the soil. You may find, however, that different ferts (with different nutrient ratios) at different times will result in more optimal outcomes. Generally speaking, higher nitrogen earlier in the growth cycle when things are heading upwards (fish and kelp emulsion is a good choice) and then switching to higher potassium and, to a lesser degree, phosphorous, when burrs start to form. Look for ferts that have a handful of micro-nutrients as well. You do seem to get what you pay for when it comes to ferts, IMO.
I found some Dr. Earth bud and bloom formula lately for my potted hops that they seem to like now that flowers are starting to set, and it wasn't too spendy.
Compost teas are also loved by plants and that provides another method to add nutrients. Try the search function--there's a lot of info out there.