Loose roof shingles

I belong to a little brick bungalow in the midwest US, built in
'54.

Contractor did a scrape and shingle back in '96 ("20 year" shingles). Missed a
spot around a vent. I took some ceiling damage before he got over to nail down
some loose shingles.

Now I got at least 2 more shingles near the peak, flappin' in the hi winds.

I am old and infirm, cannot walk the roof. Distrust my footwear, the surface,
and my balance. But I can hang off a ladder, get a little work done.

I measured: it's 13' from the edge of the roof to the loose shingles.

To secure the loose shingles, one just smears plastic roof cement underneath
and allow to cure?

I'm thinking, if I get 2 14' boards, sharpen the end of one, use that to
hold a shingle up, put a mess of cement on the end of the other, push it
up, flip it over to apply cement, I could maybe get a decent bond.

Does this sound practical? Alternatives (for a 1 man job from roofs edge)?

Thx,
Peetie