Plus one for the whacker. I use a several 8 or 10 cavity H & G moulds. I have never tried to cut the sprue by hand and don't think I will try.
I use a synthetic hammer. I have seen some like mine at Tandy Leather stores. I have used the same one for over 20 years and several of those years were when I was casting commercially. It gets a little beaten up and I will take a file to it to knock of the rough spots. It is stll very usable.
Even when using Lee six cavity moulds I keep it handy to tap out sticky boolits.
Yes I care very much about my moulds so I treat them gently. You really can't replace the 8 and 10 cavity H & G moulds anymore....Wes