Hi! I don’t know if this is too simplistic but we just use a custom field. We have a number field titled Time Spent, which people round to the nearest hour - this is only because our developments last months, with activity split into bits and pieces involving many stakeholders, so it’s difficult to be more precise. We can then run an advanced search for that custom field ‘With any value’, and narrow it down by milestone, project or individual. We have a couple of others for ‘Forecast Costs’ and ‘Actual Costs’ that do the same.
I’m sure you could probably tweak it to make it slightly more precise, but the possibility certainly exists within Asana itself.