How hard should you rub 5% minoxidil on your thinning hair?

Do not rub it in hard as this can cause damage, but Rogaine needs to be used forever to increase the hair growth and prevent its loss. I have found progesterone and PRP combination work better. There are non surgical routes for hair loss as well, I suggest seeking an expert. Best, Dr. Emer.

When using products such as minoxidil, the application should be gentle so you don't damage the native miniaturized hair. 

You should never rub anything into thinning hair which is generally more fragile than non-thinning hair. Rubbing hard will force the miniaturized hairs out, possibly forever.