If you click on the Teams link on the set you're on, it will give you a couple ways of entering teams in bulk.
One way is to get a page that lists the players without teams 10 on a page and you can update the teams that way without having to navigate countless pages.
The other way, which can be faster, is to assign a group of card numbers to one particular team. It displays the team drop down list at the top and a text box below - in the text box, one number per line, you enter the cards that belong to that team (easy with the old Fleer baseball sets!).
Other than those, unless Admin has something up his/her sleeve that they haven't shared yet....
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).