Competency is defined through the combination of 2 variables: frequency of use (never-->daily on a 5 point scale) and confidence (do not know how to use --> very confident, can teach others how to use, on a five point scale)

I have conducted more than a dozen research efforts on digital literacy of low-income populations and I can say I have not yet used the terms "comfortable use of technology", so perhaps we are looking at different things here, but I would first begin with your definition of "technology".  if you mean computers, then I would say that in order to be comfortable, one would not only need to understand basic functionality, but also the abstract ability to troubleshoot.  In order to have the ability to troubleshoot, one must first be familiar with multiple instances of a particular thing to have a basic understanding or intuition of the structure of operability.  this may sound complicated, but think of it this way - if you never used a computer before and just completed a class on basic digital literacy, you may be comfortable with the range of skills taught in the class, but as soon as something came along that was unfamiliar, a virus, a error message, a software update perhaps - that level of comfort would soon degrade.

however, if you had even a basic knowledge of computer operability, (not  super user) but had maintained this level of literacy over time, you would be more likely to have encountered similar issues, or functionality from which you could draw experience to be able to make an informed decision on how to deal with the current challenge.

put another way, the fact that I have used a computer for long enough that I have experienced several operating systems, makes learning new updates that much easier for me as I have learned where (or how) to look for something (like system settings) when needed.

I am basically describing the concept of "entrenchment" .  so if I were to try to synthesize this into a measurable metric, I would ask:

1. How long have they used the technology (years)

2.How often do they use the technology (daily, weekly, monthly)

3. How often do they seek advice assistance on the operation of the technology?

to quantify this, I would create a spectrum of technological comfort where at one end you have no comfort, and at the other end you have high level of comfort, I would then create a rubric that would outline levels of comfort along that continuum - than I would create multiple choice response options and weigh each one, and add up each respondents score in order to place them along the said continuum.

of course you will need to  justify/anchor your assertions in research, but this is the methodology I would use.

To comfort means, originally, to provide psychological and affective support to someone who is helpless. In the XVIII century and more evidently in the XIX century, an environmental metaphor appeared and the house began to be expected to provide "comfort" as in the prosa by British author Jane Austen. Comfort became an important concept in nursing, as patients are in need of support to their bodies and minds, and even social and cultural settings are influential. In Architecture, comfort is certainly a desired quality of residential buildings, hotels and hospitals (as seen by the guest and patient, respectively, not by the staff) and applies less in other environments as characterized by uncertainty to which people are willingly exposed, thus needing concentration, attention, reaction speed, some stress. The term "comfortable technology" sounds like a non-demanding technology, which allows an effortless and almost lazy operation.

Comfort or confidence as used in this survey is a reference to Albert Bandura's work on self-efficacy.