I am wondering how people get that shine like when the sun hits metal and it gets that little cross shaped gleam on it i was wondering if anyone could advise me on how to do that

Use the brush or watercolour tool, with a white or light colour and lower the transparency, opacity or alpha (it depends on the applet), as much as you want (you may need to have it not much low when you draw on dark colours and a little more low when you draw on light colours) and draw a line by "scratching" (moving back and forth) the mouse or the tablet's pen. Try to reduce the movement to the center as you keep "scratching", so that the center of the line is brighter than the edges. Then do the same with a second line placed vertically on the first one so that it creates a cross or an x. You will notice that the center area where the lines intersect is the brightest. The thickness of the brush, the length of the lines or their actual colour is up to you. >:)
|XOD|

Much thanks for the info

There's another way: First use the straight line tool to draw a bright line on a separate layer on top of the picture, then pick a large, smooth brush and use it to make the line's ends transparent with the Erase tool. At least that works in Lascaux, don't know about the other applets.