its better to pull then push, just make sure its properly sealed, you want your fan as close as possible to the exhaust port. <3 pression
if you are using a cooltube (or any air cooled hood) its better to have filter > light > fan> exhaust, theres also: inline port > light> fan> exhaust and you use a second fan filter for the odor
you want your ducting to be as straigth as possible, bending greatly reduces airflow, you also want to keep it as short as possible, also its better to have a straight pipe out of metal then a flexible duct as the flexible duct lose air flow with the curves, which make this duct solid and flexible
if you have to use a flexible duct, then use one