How to use an app to help find deep sky objects in general, either attached to a telescope as a finder scope or held on hand? A friend with a young child asked me for a beginner scope recommendation of less than $300 to see the planets as well as some brighter deep sky objects in a relatively dark suburban location. My first inclination is to recommend the Starblast 4.5 using a more novice-friendly Orion 7-21mm zoom eyepiece, but I think a major hurdle for complete beginners like her is not knowing how to star hop to find deep sky objects, and with a child around, patience is extremely limited.
With the current technologies on the night sky phone apps, I thought it might be useful and much cheaper than buying GOTO scopes to attach the phone to the manual telescope, such as a Starblast, to use as a secondary finder. I found YouTube videos about apps: 
                
             (Sky Safari Pro) or like this 
                
             (advanced app), but I don't know if amateur astronomers actually use the phone as secondary finders now. (Since I was last active with an astronomy club over 15 years ago, before any night sky phone apps became popular!) I searched online, but most web pages are not recent. So I am writing here. Do people now attach a finder-app loaded phones/iPads to telescope bodies as a secondary finder? If so, what apps do they use and does it work well (does it need frequent realignment)? I'm thinking of using a bunch of masking tape to attach the phone to the Starblast, or are there piggyback mounts I can buy for the Starblast?

If the above is not an option, I did find the Sky Safari Pro tutorial, 
                
            , where you hold the phone/pad with this app to help guide the manual telescopes to find the objects, where the biggest advantage in star hopping is that the app can flip the stars as they are shown in the upside-down view through a Newtonian scope like Starblast. For people who have tried the Sky Safari Pro tool holding the phone/pad on their hands to help with their manual scopes locate objects, is it easy to use and helpful in the field?
Are there other recommended apps helpful in finding deep sky objects?
You can do this. It's possible to mount a phone on a telescope and use it as an electronic finder with an app like Sky Safari or Stellarium Mobile.
However:

The accuracy of it very much depends on the accuracy and sensitivity of the phone's sensors, and this varies quite a lot between phones
If the telescope tube contains ferrous metal then it'll throw off the magnetic sensor
The light of the screen adversely affects your eye's night adaptation

These things may or may not be issues depending on each individual situation.
I've tried it a couple of times but never been happy with the results. The two phones I tested weren't accurate enough.
Some people do use their phones as finders, but they tend to do it with digital setting circles (DSCs) such as the Nexus 2. This has a pair of 'encoders' which you attach to your telescope, and these are used to track the movements of the telescope's axes, and update a mobile application accordingly.

Personally, I use a Telrad non-magnifying sight to get myself in the general vicinity, then move over to a magnifying finder scope, and finally to the eyepiece.
I star-hop using a combination of three, depending on my target. A lot of the time I can go straight from the Telrad to the eyepiece. Other times I'll star-hop with the finder telescope.

If your friend is short on available observing time, then it can help to plan sessions beforehand: a list of targets and directions to them from the nearest brightest recognisable star.
A program like Kstars can be used to assist with this: it has a star-hopping planning tool as well as a &quot;what's up tonight?&quot; tool.