Short answer: Less is more in the case of beard oil, since it is concentrated. Try a small amount first, and add more if required. Adding too much beard oil would give a greasy look rather than a nicely groomed appearance.
First, of all, the best time to apply beard oil is right after a shower. This is because the pore of the skin under the beard are open and the oil would be much more easily absorbed. This way, the oil can reach the hair follicles and effectively stimulate beard hair growth, and provide many health benefits including conditioning and nourishing the beard for a stronger, thicker and softer beard.
Using beard oil is not rocket science. Basically, just place a few drops into your palms, rub your palms together, and massage the oil into your beard and the skin underlying the beard. That is it. But there are a few things to consider here. First, oil is made of pure carrier and essential oils, and is very concentrated. Therefore, it is important that you use a small amount. A little goes a long way. Typically, for a small beard under an inch, use up to 5 drops of oil. For a beard longer than that, you can use about 5 to 10 drops of oil. But there is no certain rule, and you should definitely experiment and see what works best for you. But always remember that if you use too much, your beard would look greasy rather than groomed. Also, the scent in some oils is very potent and may be too much for you to handle. So less is more in the case of beard oil.
Another tip is to make sure you work the oil into your entire beard first. Massage the oil into the beard and the skin undernearth for about a minute or so.If you feel that you need more, you can always add some more. Usually, longer and thicker beards need more oil than that. We know some bearded brothers that use up to 20 drops of oil each application! It is all depends on the beard length and personal preference.
The final stage is to comb it and style as needed. Use a beard comb or brush to to comb the hair in a downwards motion so that the oil is distributed evenly throughout the entire beard. Then style your beard the way you want. The oil would give a light hold and control any annoying fly-away hairs. It would kind of weigh them down. It will also give a nice radiant, lustrous shine to your beard for a few hours.