You're right: we should keep up a steady drum beat about his refusal to show his tax returns. Which web site would you list that on?
I'm not sure which web sites. The main idea would be to work it into any op ed or letters to the editor that his refusal to show his tax returns is a strong indication that he wants to continue hiding his business interests. Indicate also that he refuses to divest himself of his businesses and is using his office for personal gain. Suggest that his travel ban is really a business move and that all of his family members appear to get special protection while jetting around on business ventures. This is why many of them have been brought in so close to government in the first place. Hack away at the idea of Russian business involvement possibly being shown in his tax returns and this could lead into that 18% area of Russian oil I've heard about.
I contend that if Cheetos tax returns are ever shown and analyzed most of the country won't want him and legislators will be prompted to take action. His lack of producing tax returns is not his vanity in wanting us to think he is more rich than he really is. It is an effort to keep us from finding out who he does business with.
The American public should keep after his tax returns in the same way that he always kept after Obama's birth certificate.