If my taxes are being done by an accountant and won't be finished by april 15th, can I use the turbo tax tool to get my banking info into the database?

NO NO NO .... doing so will mess you up horribly. 

If you cannot be filed soon then the IRS will use your 2018 return DD info for the stimulus check ... if you need to update that DD info you MUST wait for the IRS portal expected at the end of the month.   According to the IRS, they will let us know when the portal is setup:   IRS Economic Stimulus Info

Okay thanks. I'll just wait for him to do it.