If you have not been brushing your teeth habitually, it will be very difficult to get started.
Our brain does not like change.
The moment you start something new such as brushing.
Your mind will do everything it can to keep the status quo.
The key to starting a new habit is to make it easy.
It has to be ridiculously easy in order to for the new habit to stick.
One method I suggest is this.
Buy 10 good and affordable toothbrushes.
Place everywhere in your house.
Especially spots where you spend most of your time.
For example, the couches you sit to watch netflix, the table right next to your bed, and etc.
After a few days, you may find yourself holding on to the toothbrushes and actually brushing your teeth in front of the mirror in the restroom.
Soon you will realize if actually feels great to have a clean teeth.
Your brain will tell you that it is beneficial for you to keep your teeth clean and send cues to you
that you should get brushing everyday!
Let me know if this has worked for you.