How do i know if what I'm drawing is 512x
could i just print These pictures and compare

You could do that.

Alternatly you could draw the textures, then scan them and shrink them to the correct size.

But then it would lose some of its handdrawn ness making it ugly

Unless you have a good scanner with high pixel rate, it wont when you resize it.

well no matter how nicely you draw it it will still look pretty bad in digital form. and yes i have tested it. i have ended in completely redoing the head i photoshop.

You could use a graphics tablet, and photoshop. Using a brush set, that gives you a realistic "hand-drawn" feel to it. It's still hand drawn, but done on the computer. ^_^

printing the templates wont make a difference, when you scan in the print, it will still look bigger.
you have to scale your sketch down in gimp/photoshop.
you cant even do the maths to fix it, cus the printer would just fit it to the page.

ive only seen one person make good textures out of scanned in pencil sketches. Cant remember his name tho, it was way too long ago