You've finished that painting, so now what?
Here are 5 things you should do after you finish.
1) paint another piece
2) paint another one
3) and another
4) repeat step 1
5) repeat this for the rest of your life
If you want to make money from your work, then you will need to show people and tell them it's for sale. You can do this by uploading on your website and posting on Facebook, Twitter, and a blog. If you have a newsletter with subscribers, then send them a picture of your new works and how much they cost.
If you want to write about the painting, or the process, or something, then you should do that. If you don't want to, then don't.
The point is, you are an artist and your job is to make art. Don't listen to marketers who aren't artists. And those marketers who are artists, take their advice with a grain of salt.