Hiding specific files in Ubuntu and Mint is done by placing a dot (.) in front of their name, e.g. renaming the file muh to .muh will mark it as hidden and render it invisible the next time you open its directory (this does not work on the desktop).
To make files hidden without altering their name, create a new document called .hidden in the folder where the files that you want to hide are located. Enter the names of the files into the document, one name per line, then save it. Open the target folder to check if it worked.
To make hidden files visible, simply hit Ctrl + H.