Quick question, sorry if this is a repeat of elsewhere but I couldn't find anything obvious about it. What varnish/topcoat does everyone use/recommend and why?
Testors Dulcoat is allways a good choice, uses a coat of gloss or semi-gloss under it for extra durability.
I've been using Army Painter's Quickshade on a lot of my more recent projects, and it acts as a pretty decent gloss varnish as well as shading. It has preserved my paint jobs really well (as well as provided shading for a lazy painter such as myself)! The downside of course is if you actually are good at painting (unlike me) and don't want your models to look "dipped" it's not for you. It's also very messy to work with if you "dip", and ruins your brushes if you paint it on. It takes a long time to dry and has a habit of pooling (as it's supposed to, but if you're not careful you can ruin your models) and gets really sticky. I also have a really old spray can of Games Workshop's Gloss Varnish. It works well but you have to be careful - too little and you end up looking grainy, too much and it's blobby. I don't think they actually make it anymore, so it may be a moot point.
1) Krylon Crystal Clear Acrylic -- 2 coats for metal models, 1 coat for plastic/resin This is a spray gloss that does an excellent job protecting the paint from chipping on metal models. Plastic models don't really need as much protection since they both weigh less (not as much impact when they fall) and primer adheres better making the paint more durable. But I still use this product on plastic models. I find that using a matte finish by itself can substantially change the look of underlying paint, especially metallics. This acrylic gloss does a great job of protecting the look of the underlying paint. Two light coats are better than 1 heavy coat to avoid dripping/pooling. 2) Matte spray (any brand) -- 1 coat After the gloss completely dries, a coat of matte spray kills the shine. I have not found a real difference in matte sprays. Use the cheapest you can get your hands on.