Greetings from the other side of the pond !
I would not worry so much about the nozzles clogging up just leave them in the presto pots or at least that’s what I do . As far as the block I usually clean mine out inbetween rounds.. On a side note I put my dual injector and block on a skillet to get them close to temp before I run anything through them.
I have never personally used silicone but I have used pop to make injection molds