Well, I am not Griff, but if you do not mind, I will give you a bit of advice regarding the use of guitar picks.
I have found that about 85% of guitar instructors are incompetent. Do it my way or the hiway is their moto.
In the end you will have to find what works for you, but you are going to have to do your homework!
Holding and using a pick while strumming and picking are a bit different. You even get into what thickness pick to use for these two very different techniques. People with such suggestions may not realize that the piece of music you are playing could require both techniques, and it is not "easy" to change a pick in the middle of a piece of music!
There are several factors to consider:
1. The guitar you are using.
2. The pick itself.
Try looking at several YouTube offerings about using a guitar pick. Attempt to emulate what is shown and use what works for you.
Pick control is very important. My suggestion is to use a major or minor scale, or even a part of a scale to begin with. Start with open strings and work your way up the neck, over a period of a few days.
At first use all downstrokes. Then add alternate strokes down - up. Finally, add triplets. You want to get the "feel of the pick and strings".
Practice and see what works best for you.
Some "pickers", like Jerry Reed, develop his/her own style of holding a guitar pick. Find what works for you, and with a good deal of practice you will be comfortable with what you are trying to accomplish.
Tom