I used masking frequently in the early days. I was concerned that total masking would mess with habituation (as Michael Leigh mentions), so I used partial masking at night for sleeping, but total masking during the day totally helped me get through the first few weeks. I found that I could completely shut off the tinnitus by listening to a crickets-like sound, it worked even at very low volume. Being able to halt the noise gives you one less thing to worry about while you wrap your mind around what is happening to you. I don't think that this is bad to do, as long as the volume level is low and you don't notice any "backlash" from your tinnitus after you stop the sound — the worst that it can do is delay habituation.
Partial masking (a sound that you can hear your tinnitus over) is better if habituation is your goal (which I think it should be unless you are confident that your tinnitus is short-term). As you get more accustomed to it over the weeks, you can lower the volume of your masking sound, until you don't need it anymore.
I got to the point where I could stop using masking during the day at about seven weeks in (granted, my tinnitus eased up a bit and that helped), though I do sleep with plain noise still.
Be careful with earbuds and keep the volume low.