"Old and decrepid. Bad shoulders, knees etc." Hi there. At last I have found fellow sufferers. Old and decrpid...that's me 77 and I can't rearrange the numbers. Yes. I also have my fair share of disabilities.
Now back to the original. Fair do's I have worked with commercial parks machinary. Now in your garden. Depending of course on the size of your lawn. Manual spiking and scarifying, every time. Scarifying. A basic lawn rake will do. The idea is to remove the thatch from the grass. Then the aeation. A common garden fork will do, but a hollow tined fork is better. The latter will take out cores of soil. This will enable sharp and to be brushed across the lawn, the sand sinking and filling the holes. This will allow free drainage and sub-soil ventilation.
Marketwise. This spiker will rejuvinate your lawn. RUBBISH. Garden macinary on offer to the public is mere gimmicary. Spikers, rotovators etc. The machine lacks weight. A rotorvator simply rough up what? three to four inches of soil surface. Manually a spade or fork will turn over 12 inches of soil.
In pactice. Set a line say three to four feet wide. Now working backwards, either rake..scarify or aereate. Then measure a further area. In comparison youy will find the manual method best.