Adding custom fonts to the Promotional Popup

Hello!

So, I've had quite a lot of success being able to change the fonts across my site with CSS depending on the block used. However, I cannot get this to apply to the Promotional Popup.

For example, I currently have the following:

h1, h1 a, h1 blog title, entry-title {
font-family: 'Wilderness';
}

So that my blog titles etc are all my custom h1 font. However, this does not seem to be overriding within the popup and it is maintaining the font listed in the Site Styles.

Is there a special identifier such as "h1 promotional" that can be used? I've tried using an inspect field in chrome to determine the data range, but using ".sqs-slide-wrapper", ".sqs-slice-heading" and ".sqs-popup-overlay" seem to have no affect.

Any help is greatly appreciated!