Fork needles can be perfect for monorooting, and are recommended for more experienced artists working on vinyl dolls.
The main benefit of the forked needle, is that there is a small slit at the end of the needle, rather than barbs up the length. This means that there is much less damage to the vinyl when using a forked needle compared to a crown. If you're frustrated by seeing white marks where the crown needle enters (as can happen with some varnishes), try a forked needle instead.