Priming the engine and Mag check questions

I have an old tired engine in my plane that requires 7 strokes of prime
no matter what, cold hot or warm. No biggie, as it starts everytime
within 3 turns of the prop. I don't have to crank for any period of
time. A person told me it is better to push the primer slowly rather
then quick shots. Mechanically inclined I am not, but does it make a
difference? I have not noticed any difference trying it either way.

Mag check. On runup, I check both mags by flipping the switch to mag
one and mag two. Another person said I should hesitate before going
back to both mags when checking the mags. He says that I should let it
run on one mag for 3 or 4 seconds. All I am checking for is the drop.
Is there a benefit to letting the engine run on one set of mags for a
period of time during the runup?

Thanks for any input.

Allen