I use dektol, but the ones that come in liquid concentrate are easier to mix, and you avoid the possibility of inhaling the dust.

I also use a fair amount of Ilford postcard stock, good stuff, and as good as anything to practice on too - one thing though, the RC coating makes it difficult to write on. The most effective thing that I have found is a fine point sharpie - for things like invitations I make up stickers with mailing labels and just stick them on.