Varnishing sounds intimidating, but it is really quite easy. Just lay some plastic or a drop cloth over your work surface and get a good brush. That is all you need. I use Gamblin Gamvar varnish. It is easy to use, can be removed with mineral spirits and the smell doesn't make you feel like you want to pass out. The Gamblin website has a short video of the process that is very helpful if you haven't varnished before and want to give it a try.
Once you get your supplies together, it is time to bring the paintings outside. The first step: clean the painting with an old T-shirt to get any dust off of the surface. Then put the painting in a sunny spot to check for dust again. If there is any left you will see it right away. When there is stubborn dust that won't come off with the rag, roll a piece of blue painters tape into a circle and roll it over the painting. Gregg taught me this trick when my landscape fell face down in the dirt.
When that step is completed it is time to apply the varnish. I got this wide mouthed jar at The Container Store and it works great, but you can use a plastic cup in a pinch. Just make sure you have a funnel to put the unused varnish back in the bottle.
This is the painting after I completed the varnishing. It is easiest to work in an assembly line and just get them all done at once since this project is so dependent on the weather.
I went over this painting with the blue tape and then varnished (notice my classy paint stained pants!)
I thought this painting was fine after dusting. Good thing I put it in the sun because sure enough there was dust all over.
I use a large brush and apply one coat of varnish. I follow the technique in the Gamblin video and it works great.
One last caveat, make sure the painting you are varnishing is dry to the touch. Gamblin recommends waiting three to six months before varnishing and I think that is a good rule of thumb, but I've done it at two months and did not have any problems.
If you have any questions about varnishing or cleaning paintings, leave me a comment. I'll do my best to help. (As usual, I didn't receive any comps from these companies. I'm just a satisfied customer).