I've done it multiple ways:
1. Modeled in the grating (only on fairly small parts)
2. Use a hatch pattern
3. Create a sketch of the grating and save it as a block that can be dropped into place.
yes, grating modelling takes too much memory.
the method 3 is not flexible.
I would like to use method 2 you mentioned. thanks
I prefer and do 2 and 3. No modeling.