Everyone has ALL of the Zodiac Signs within them. Which is why you can find ALL of the Zodiac Signs in EVERY Birth Chart. Even if the House of a Sign is empty (meaning, if you have no Planets in a Sign) the House still exists and therefore you can work with it.
For Example: Let's say Cancer is over your 1st House. And you have no Planets in that House. Cancer is still over your 1st House. And so you can work with Cancerian energies when dealing with 1st House matters... Identity, Physical Appearance, Personality... Maybe you have a pale or round face, maybe your mood or opinions changes frequently, maybe you disappear often or go through phases of (not) showing up for yourself and others.
So it goes beyond your Sun, Moon, and Rising Signs. And in addition to empty Houses, you can apply that concept to every Planet in your Chart because it too is located in a Sign and a House. Your Jupiter is located in a House and Sign. Your Mars. Your Venus...
When working with the Zodiac Oils or the Planetary Dressed Candles, first think about what you want to target about yourself, then find out what Planet or House or Sign rules that thing, and then look to your Birth Chart to see where/how those things are personally relevant.
For Example: Resources, Possessions, Abilities...2nd House/Taurus/Venus. Siblings, Nearby community, Early education..3rd House/Gemini/Mercury and so on.