If you want to have the use of it for a long time you have to clean it realy well every time you used it. I assume you used it to paint oil based paint in which case you have to use the same liquid that you used to thin the paint, like therpentyne or thinners. After washing the excess paint out, blow some of the thinners through - about 200ml. To make sure there is no paint inside on the needle and the spring, take the bits out and make sure they are clean. You can spray it with some 3-in-1 oil to make sure it's not stuck when you want to use it again. It might not be practical for you with this model but I always left some of the thinning liquid in the bottle. Also, if it is possible, I took the nossle off and left it in the this bit of thinning liquid.