The WTFPL is a license that basically puts the work licensed with it under Public Domain. That is possible and there are multiple ways to do so.
Basically putting a work into public domain allows everyone to use it as he sees fit. That is the same as the WTFPL claims. This also fulfills your requirements as you put them in the OP.
One point here that needs some elaboration is the right to get attributed. While a Public Domain work asserts no rights for the author, it still is needed in some countries (like germany) to acknowledge the original author of the work (otherwise you are plagiarizing). So depending on the jurisdiction someone making a derivate of your public domain work may still put some acknowledgement to you. That is called moral rights, it may also (depending on jurisdiction) include the right, that your work isn't used to belittle or defame you.
Another point often brought forward is the liability for damages your work creates. Many people recommend to put a disclaimer to deny all liability, something like this example:
This documentation is provided on an “as is” basis, without warranty of any kind. Use at your own risk! Under no circumstances shall the author(s) or contributor(s) be liable for damages resulting directly or indirectly from the use or non-use of this documentation.
While such a disclaimer seems useful, it most likely does nothing. In most jurisdictions you cannot with a simple disclaimer avoid to be responsible for gross carelessness. At the same time any user of your work who get damages through the usage cannot just shift the responsibility to you, if you avoided major carelessness. In many cases a warning about possibilities of misuse that lead to damages may be enough to avoid being accountable. So the usefulness of such a disclaimer is low.
The WTFPL doesn't use such an disclaimer, but you're free to add one yourself, if you feel the need for it. As I explained, it will not do much, but depending on your jurisdiction it may have a bit of influence.
Lastly it may be pointed out, that child filters may restrict the availability of your work, if the inclusion of the license leads to the inclusion of the language that is considered strong by some. I personally wouldn't care, but if you do, you should use another way to put your work into public domain. Your OP says, that you don't really care either, so WTFPL is OK.
There are some other ways to put your work into public domain:
- You can just state, that this work is put into the public domain. You can add or not add a disclaimer to be not liable for any damages your work causes.
- You can use the CC0 license from Creative Commons to declare your work as public domain.
Is a permissive license an alternative?
A permissive license like the MIT license or the BSD license granting the user a lot of rights, but they still reserve some for the original author. The WTFPL and other public domain dedications give the user more rights. If you think about the WTFPL the usual permissive open source licenses are more restrictive. Still, your requirements as you put them in the OP are also fulfilled by typical permissive licenses, they allow usage in a closed source project, allow reselling your work and allow the usage for any purpose. So depending how important the rights they still retain are for you, they may be an alternative.
TL;DR: Go ahead, use the WTFPL.