If you want to use the LCDUI for drawing thicker lines have you tried drawing several lines side by side. And for other shapes(rect, cricle etc.) draw a smaller shape inside the original one with the same background color . For example...
// background fill
int x1 = 30; int y1 = 30; int x2 = 230; int y2 = 230;
// draw three lines side by side
for(int i = -1 ;i<2;i++)
// if(x1>x2) etc...
// draw a circle and then fill it with a smaller circle with the same background color.
g.fillRoundRect(60, 140, 60, 60, 60, 60);
g.fillRoundRect(65, 145, 50, 50, 60, 60);