Yea, fert spikes as you describe are the same way I do outdoor and indoor with only a small difference, I put a layer of fresh soil in the bottom of the bucket or hole. I take a clump of my organic fert mix, bat guano, sea bird guano, composted cow manure, compost, chicken shit, wood ash, green sand, gypsum, mycos, ground oyster shells, seaweed, fish emulsion, iron shavings, and a few other things i cant think of right now (I like to single out all the and macro and micro nutes and find a source for each) and whatever else your heart desires. place it directly under where the root ball is going to be. and always cover with another layer of fresh soil so the roots can grow into the fert mix. This work well with plant age and the cycle outdoors. It will take a few weeks for the roots to be fully involved with the fert mix, just in time when the plants start grabing nutes and striping the soil, there is an abundance of nutes and metals for them to feed on. Outdoor this is the best way ive found to limit the leaching of nutes during rain storms and such. If I took the same amount of fert, mixed it with all the soil, the plants do not get even close to the size and quality of the fert clump under the root ball. And I must add AACT teas are the best way to feed, in any of my experience.
for the og grow i did, I used super natural fertilizer and some of the additives from them as well as the fert mix i described above, they loved it!! outside they really sucked tho, bud rot was everywhere, loose airy bud, and it was so leafy i made bubble hash, and tincture out of most of it. the plants were only 4-6 ft. and were dwarfted by my white russians that were 12 ft untended. good luck man