If you want grainy shadows, the trick is to snatch the print before the blacks set in. When you have the first black dots which multiply , be extra vigilant and check with a small torch ligt (with a red filter of course) and snatch the print when you judge the effect is satisfying.
But Mark's remark is right too, some papers will give you more grainy pictures than others, I do not know about Slavich but I know Emaks papers do give grainy pictures.
Angelo