Hi,
Welcome to SRP! I also have a goatee-- took me a while to figure out which strokes to use.
When I do my initial WTH strokes down my cheek, as I get closer to the goatee line I concentrate on using the heel of the razor-- but I'll clean up the line later, so I don't worry about getting too close.
When I do XTG passes on my cheek (with toe up, heel down), I start near my ear, and stroke towards the goatee, letting the goatee stop the blade.
After I'm done shaving my entire face, I come back to the goatee to clean it up. I put the edge of the razor on the goatee line, and shave *away*. For the upper lip, I hold the razor tangs on the sides, blade up, and shave up and away. As I move along the goatee line, I change my grip so I'm holding the tang top and bottom, toe up, heel down, with the edge of the razor on the goatee line, and shave away, stroking towards my ear. Same idea for under the chin.
As for the neck, there are two critical things-- first, you need to figure out which way your hair grows, second, you need to stretch the skin correctly. For me, my neck hair grows in two different directions. The hair on the top half of my neck grows generally down, and the hair on the bottom half of my neck generally grows up. I do two passes, in 4 parts. For the first pass, I start with the upper neck, shaving down to the point where my hair changes direction (about halfway down). For the lower neck, I shave up, stopping at the same point. For the second pass, I do the opposite. Since my hair does not grow *exactly* up and down, this ends up being two XTG passes, but from opposite directions (I don't to do a third ATG pass on my neck).
When shaving, you should stretch the skin in the opposite direction to how the hair grows. So on my upper neck, I put my fingers on my chin and lift up. For my lower neck, I put my fingers on my lower neck and pull the skin down.
When I'm done, I use a dose of Nivia Balm for Sensitive Skin.
Good luck!
-Chief