How to set the values ​​of a Bitrix custom field in bulk?

Question

1C-Bitrix

Good afternoon! Colleagues, tell me, please, how to massively set values ​​to a custom field. There is a highly loaded online store on Bitrix. It has 1500 sections and subsections. There is a custom field with teasers. As I understand teasers-highload-block, directory-infoblock. Communication is carried out through the user field. It is necessary to set a certain value for this field for all sections and subsections, that is, select certain teasers for display.