Two suggestions :

1) You can get plastic razor blades for this purpose.

2) A carbide scraper. You pull it, instead of pushing it, which makes it less likely to gouge deep scratches.

 

I've just read online that gasoline or lighter fluid dissolves RTV successfully. I used both cellulose thinners and brake cleaner with some limited success. Unfortunately it seems whatever one uses it still remains a lot of boring hard work to finally clean it all off. RTV is great stuff provided it used where it's easy to remove later and used sparingly. (I over used it on the rocker cover gasket out of frustration to stop the oil leaks on the Pajero )

 

Plastic putty knifes

 

I used to grind the end of a good flat file at a slight angle. Need to be very careful on aluminum as mentioned to prevent gouging.

 

Carb cleaner.
Spray the crap out of it.
Comes right off with STP carb cleaner from the auto parts store.
Wear gloves though.
Stuff will poison you and is probably the cause of toxic waste dumps.
SO be careful.