Using Mercurial (hg), can you just "hg backout" all the commits you did for the files you don't want to push, and then do a push?

Because Mercurial (or Git) won't let us push a single file or a single folder to another repository, so I am thinking:

1) How about, we just look at the commit we did, and hg backout the ones we don't want to push.

2) hg out -v to see the list of files that will be pushed

3) now do the push by hg push

Is this a good way?

This is because I got the following advice:

1) Don't commit that file if you don't want it to be pushed (but sometimes even just for experimentation, I do want to keep the intermediate revisions) (-- maybe I can hg commit and hg backout right away to prevent it from being pushed.)

2) Some people told me just to hg clone tmp from that repository i want to push to, and then copy the local file over to this tmp working directory, hg commit to this tmp repository, and then do a push. But I found that the hg clone tmp will take up 400MB of new data and files, and make the hard drive work very hard, just to push 1 file? So I would rather not use this method.