It is indeed annoying to remove all your introduced woody weeds from your wirra just to watch a massive explosion of new woody weeds appear. In fact there seem to be more new plants than was just removed. This is normally the case.
When a plant is growing it produces various chemicals, called pheromones, which are interpreted by other plants around and imparts to them all sorts of knowledge. When you clear the woody weeds then the ceasing of the production of these pheromones is interpreted as an event which tells the seed-bank in the soil to germinate.
Plants have evolved in a way that they produce seeds that store in the soil for varying times. When an event occurs that tell them it is time to germinate only a certain percentage germinates. The others wait for another event. In theory there is no limit to how long seeds can remain in the soil and then successfully germinate.
While this may be very annoying in the case of plants that you do not want, it is precisely this ability of seeds to remain dormant in the soil that allows the successful restoration of your wirra.
Plants that grew there many years ago deposited their seed-bank in the soil. If an event occurs that suits their germination then some may germinate. When you develop your wirra you will need to experiment with different events to see what you can get to grow.
You will also need to experiment with events to try to get some plants to flower and seed. It has taken me ten years to work out how to get my tall leek orchids to flower. However I succeeded this year. Normally these orchids flower after fire but I didn't want to use that method.
Collecting seeds is an important part of developing your wirra. When you have a list of all the plants that should be growing in your wirra, you will need to collect seeds from your nearest occurrence and cast them on your wirra.