You don't need daily practice to know a magnifying glass under the sun can start fires, this is public knowledge, who the fuck is practicing that.

Also, it's be much more efficient and reasonable to just use a lighter, alternatively

if you wanted to attempt to make this imagery work, starting a fire with wood rubbing would be extremely inefficient, however extremely practical in survival situations. Because it's inefficient, it takes practice to get good at it.

No need to thank me