get sth to do 和get sth doing有何区别

据我了解，我们一般只说get sb. to do,如 I will get him to finish the job.get 后面的宾语是不定式的主语，就是 he finish the job.
而get sth doing和get sth done 是和句子中的时间状语有关的。如 Tom got the problem solved before dark.
如果时间状语强调现在正在进行的，就用get sth doing。但说真的，我几乎没见过get sth doing的形式。
PS:我是上海今年的应届毕业生。

get sth. doing:
bring sb. or sth.to the point where he /it is doing sth.是人或物达到动作之某一点
Can you really get that old car going again?
It's not hard to get the child talking.
get sth to do
使人或物以某种方式做某事或行动
I can't get the old radio to work.
You will never get him to understand.
get sth. done完成某事,作好某事

to do指将要做得事
doing已做或正在做