In Feed Tool > Modify Products there are two unique attributes in your Sales & Orders accounts:
Exclude From Feed
Include In Feed
Essentially, they both function in a similar fashion, allowing you to create Filters for either excluding products from select or all channel feeds or, conversely, including products in select or all channel feeds.
Both are Filter Only rule types thus there is no attribute to be set:
Your first step is to create your desired filter, and in this example we are using:
Price > Less Than > 5 - Exclude From Feed which will exclude ALL PRODUCTS that meet this criteria
Note that if you were to use Include In Feed the same rule would force your feed to only contain ALL PRODUCTS with a price less than 5
After creating your filter, you'll then need to select which Product Channels you wish to have this rule applied to:
Note that you can create unique rules per channel or apply the same rule to multiple channels
Pricing Tool: This channel should be used on its own when subscribed to a Repricer plan, thus allowing you to filter out specific products to only be run against competitors
Once you are satisfied with your settings click Save. You can then scroll down to preview your Rule:
As with any Modify Products Rule, you must Send Feed to have them applied to your desired channels.
Navigate to Feeds tab > Feeds panel and click Send Feed. Note that you'll have to send each channel separately: