Sometimes a trip the to the local Art Supply store can be helpful for your modelling endeavours. As modelling involves alot of painting sometimes, there are some interesting things, and products, that can be found at the art store.
A few things I have noticed in visiting the Art store is that there is a wider selection of brushes to select from, and in some case, they may be cheaper than the hobby store. Not only brushes, but other tools can be found there too, for example I use a paint knife to apply putty, great little tool.
The key to a great finish is getting the paint to lay smooth when applied. Two products that I have found at the local art supply are from Liquitex, Flow Aid and Slo-Dri. Flow Aid is a product that helps in allowing acrylic paint to flow better and penetrate uneven surfaces, while Slo-Dri is just like is says, it slows down the drying time of acrylic paint.
For Flow Aid, I mix a small bottle with about a cap full mixed with water. I use this mixture as a thinner when working with acrylic paints. I mostly use Vallejo paints, and find it works great. I also find it handy to use when applying washes, as Flow Aid will help break the surface tension of water.
Another item you can find at the art store is paint. Some hobby weathering products can be a little expensive, one product I have found is Winsor & Newton Water Based Oil paints. Yes, I said water-based oil paint. This paint is great for doing washes and filters, and being water based makes it easy to clean and relatively fast to dry. I will use my Flow Aid mixture to thin this, and a tube will last forever.
Once you are done all the painting, it is time to clean up. Overtime, old paint can build up in a brush regardless how well you clean it. Well another product from Winsor & Newton is Brush Restorer. This stuff will eat away at all the old paint in a brush, and if you are not careful the finishing of the brush too. Use a small jar and only pour in a depth just higher than the bristles, soak the brush for about 15 minutes, then work the bristles gently between your fingers. Once you are satisfied, rinse with water, and the brush will be like brand new.
So get out of the hobby store sometimes, and head to the art store, you will never know what you will find.