Call me conservative, but I go up my mast solo using both a climbing harness AND a bosun's chair and TWO halyards.
NEVER go up with just one halyard. If you do that and your halyard fails, you probably DIE!
The primary halyard is attached to to the bosun’s chair’s as shown in the picture.
This arrangement requires two ascenders, a regular climbing ascender for the foot straps and a micocender for the bosun's chair. To ascend, sitting in the bosun's chair you grab the line above you as high as you can with one hand near but above the other. Then you stand up against the foot straps and hold onto the line.
I tie my climbing harness to the secondary (backup) halyard using a Prusik knot, which can slide easily up and down.
This setup works well when single handed and does not require any great strength to ascend the mast.