The most safe way is probably by enrolling into a forum signature campaign, they pay out weekly and all have their own specific rules, nothing too difficult to understand.
By growing he probably means investing somewhere and then they should grow gradually and for that there are things like trading or casino bankrolls etc, if he is also talking about ways of earning then yes, signature campaigns can be the safest if someone learns all about them and knows something about bitcoin.
If we think of safest way to grow bitcoins then it can be done only with signature campaign as you will be paid regularly for the work that you have done, so you can treat it as a regular part time salary.
Only way to grow them is by investing them. And that's never 100% safe.