How to rate limit processes started by incron?

Hi,

if I wanted to scp each file that is written within a certain
directory I'd use an incrontab line like

/home/sync/ IN_CLOSE_WRITE /usr/bin/scp $@$# sync_at_anotherhost

I'm also using SSH ControlMaster so that I do not open more than one
ssh connection (the Master is opened by Autossh beforehand).

Problem:

Unfortunately someone copies 30 thousand files to /home/sync which
results in a lot of processes and a lot of things go wrong then. How
do I can I solve this?

telling incron to not start things in parallel or only a certain
amount of parallel processes?
queueing with anything else?

thank you reading my mail and thank you in advance for your answers :)

-- 
CSI