I have tried keeping an old pair of pants - I forget to put them on and can't be bothered to go downstairs and change. I do have a woodwork apron, but more often than not I have left it in my woodshed. My solution is to keep an old towel on the arm of my modelling chair and put that across my legs while working. Not too elegant, but it works for me and is quite good at catching those tiny parts which get dropped.