As a note the fleshlight are really tight. I have a can one and it is as difficult as anal to begin with.
Although it still depends on individual girth, the fleshlight sleeves come in different sizes. I have a 'classic' smooth one, which was very comfortable to use from day one. I then bought a very tight 'anal' one, which was so tight that I only used it twice (once upon getting it, and then once more to make sure that it really wasn't going to get any better).
I can actually turn the classic one inside out without forcing it, when cleaning, the material is that soft and pliable.
Having made multiple posts on a male sex toy thread, I think I've well and truly labelled myself a wanker.