Hold it at the datum attitude....using the cowling and horizon for reference. If you can't feel if you're pushing or pulling - simply let go of the controls briefly.... what does the nose do? If the nose tends to rise you need to trim more nose down... ie wind the wheel forwards. If the nose drops you need to wind the wheel backwards.
It only requires you to momentarily let go of the wheel - just to work out what the nose of the a/c wants to do left to it's own devices.
It'll come to you - just takes a bit of practise. It's also far easier to work out on a smooth day.