Since everyone has different preferences we can't say what, specificially, might give you more enjoyment; your best option is probably to vary the types of touch, pressure or positions you're using while masturbating and see what feels good to you.
You can certainly introduce a sex toy into your masturbation if you'd like, as a sex toy can add new kinds of sensations, but you don't necessarily need to do so. Again, it all depends on what feels right for your body,
That site is not credible: it never has been. There are others just like it. They are bunk. If you take time to really look through that site, you will find a world of inaccurate or seriously outdated information.
It is not unhealthy to masturbate in any position, including being prone.
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead