Try cleaning while the top is still hot.
Cold will close the pores and cause retention of a lot of the gunk.
Then when it is turned back on the pores reopen and everything will ooze back out.
Learned this during a short stint at the Loop 410 (north) Toddle House in San Antonio.
Cook taught me how to season and maintain pans as well as the flat top.
Was way underage and this was on the juke box https://search.yahoo.com/yhs/search?p=bye+bye+miss+american+pie+song&fr=yfp-t-900&hspart=att&hsimp=yhs-att_001&type=att_pc_homerun_portal