You will receive notifications as bids come in. From the Settings section, you'll see that you can notify previous bidders via text, email, or both. This will notify the bidder when they have been outbid, and there will be a "place new bid" button in the email/text that will take them back to the auction page to place a new bid if they choose to do so:
Pay With Check
The auction settings also allows the ability to allow winning bidders to chose the option to pay with check.
Once Pay With Check is enabled, an editor will open and that will allow you to enter any content in there to display to them. This can be used for instructions on mailing address, check payable, etc.
If you would like the person paying with a check to download an invoice, you must visit the invoice settings in the Payment Section of your event dashboard.