Conditional Formatting - reference to other cells

My conditional formatting formula is ="if(and($K3="""",$J3<(today())"

Problem is I need to copy that conditional format to the rest of the spreadsheet. When I use the Format Painter, the next row has the same conditional format. It needs to be ="if(and($K4="""",$J4<(today())"

Any way of getting excel to fill the series in conditional format??

I don't think you have quite the right formula. Excel should adjust the rows automatically but it appears that quotes have been added to the formula by excel. Try just

=and($K3="",$J3<today())

If you select the whole range you want to format before you apply the conditional formatting then you don't need to use the format painter at all

Are you actually using the Formula is option?