This may be too old school for some but I boiled willow bark down to a tea and used it, it has a natural rooting hormone in it, so basically I drop in a rapid rooter, squeeze excess out and pop in my clone put the humidity lid on and mist the rooter's with the willow bark spray as needed. Seemed to always work well for me when I cloned for outdoor guerrilla grows.
"“Willow Water” is a homebrew plant rooting hormone that is easily made and can be used to increase the strike rate (growth of roots) of cuttings that you’re trying to propagate.
The way that it works can be attributed to two substances that can be found within the Salix (Willow) species, namely, indolebutyric acid (IBA) and Salicylic acid (SA).
Indolebutyric acid (IBA) is a plant hormone that stimulates root growth. It is present in high concentrations in the growing tips of willow branches. By using the actively growing parts of a willow branch, cutting them, and soaking them in water, you can get significant quantities of IBA to leach out into the water.
Salicylic acid (SA) (which is a chemical similar to the headache medicine Aspirin) is a plant hormone which is involved in signalling a plant’s defences, it is involved in the process of “systemic acquired resistance” (SAR) – where an attack on one part of the plant induces a resistance response to pathogens (triggers the plant’s internal defences) in other parts of the plant. It can also trigger a defence response in nearby plants by converting the salicylic acid into a volatile chemical form.
When you make willow water, both salicylic acid and IBA leach into the water, and both have a beneficial effect when used for the propagation of cuttings. One of the biggest threats to newly propagated cuttings is infection by bacteria and fungi. Salicylic acid helps plants to fight off infection, and can thus give cuttings a better chance of survival. Plants, when attacked by infectious agents, often do not produce salicylic acid quickly enough to defend themselves, so providing the acid in water can be particularly beneficial.
Willow water can be made from cuttings of any tree or shrub of the willow family, a group of plants with the scientific name of Salix. The more cuttings that are used and the longer they are soaked in water, the stronger will be the resulting willow water. Recommendations for the exact method of soaking vary. Cold water can be used, and soaking times of four or more weeks are often quoted. Other gardeners use boiling water to steep the willow twigs and soak the mixture for around 24 hours. " - author unknown.
