Has anyone successfully been able to report on current days in process for a project? I'm basically looking to show how many days a project has been in process from the start date. Seems simple, but I've been told that there isn't a way to do this!

Super simple. I would just do a calculated field in a custom form. You'll need to make sure that custom form is applied to the projects you want to see this on.

Here is the calculation:

WEEKDAYDIFF(Entry Date,$$TODAY)

Here is a doc on creating calculated fields: https://one.workfront.com/s/document-item?bundleId=the-new-workfront-experience&topicId=Content%2FReports_and_Dashboards%2FReports%2FCalc_Cstm_Data-Reports%2Fcalculated-custom-fields-calculated-columns.html&_LANG=en

You could also do a calculated column in a report, but the benefits of having this in a custom form are pretty significant.