I've just filtered some Tayberry gin I've had on the go for 3 months. Simple to do. 1 litre thermos, 4 oz on sugar, add 1 pt of gin, bang in as many tayberries as you can till it's up to the top. Shake daily. Leave for 3 months. It's well nice.
I have read it's better not to add sugar at the start as it stops the natural sugars of the fruit being absorbed, but it tastes grand the way I do it. Start on some sloe gin tomorrrow.