You can lean a padded ladder on the side and get to most of the roof area. If you do go up, keep all weight (knees/hands) on rivet lines and wear shoes that will NOT slip.
Now, here is one I learned the hard way...DO NOT lean any weight on your very brittle A/C cover
or your hand could go right through it....
Having said that, I go up yearly and take a spray wax with me and clean off any dirt/mold and wax at the same time while inspecting sealants around everything. Did I mention not to lean on the A/C vent at all...It looks so tempting to just lean for a second or two, don't do it. The A/C vent cover gets very brittle from the sun.
I actually have to seal my refrigerator vent cover tomorrow and will seal the heat shield while I am motivated. Two good places you should inspect! This job will be done from a ladder, not the roof. Easy to access from the side and I work better when standing than kneeling.
Some people have built a carpeted board that links between rivet lines (frame supports). That sounds good for the knees, but I have not put one together yet.
Good luck and remember to take all your tools/sealants with you the first time