You may need some Methyl Hydrate (Methanol) to flush that tank. Any good hardware store should have that but wear gloves, not good absorbed through skin that the Methanol. May take a little while for it to release the silicone but should work. I have some rubber parts treated like that in my test jar...I'll look later.
Sure it is silicone??? If blue and a little sticky could be Hylomar,not much will touch and clean that. Long soak in Methanol maybe....again I should look at my tests.
If silicone I'd be weary, some aren't "sensor safe". Doesn't take much of that to pollute an O2 sensor if so equipped. And in any case none of them silicones are fuel proof, bad choice around fuel systems.Fuel resistant maybe once dried and outside of the system, but sure not so when exposed to gasoline.
Getting rid of the gas or water.....stick paper towels in there,long lenght keeping one end out. Should wick everything out.
I think Gates now has hose that will do both, in or out of the gasoline. Came upon that not long ago.
If not make sure you get Spec 9 and 10.They don't interchange.