I primarily use Amaco underglazes as well as some English underglazes and the newer Spectrum underglazes. I mostly use the Amaco pan sets, sprinkling in water to soften the underglazes before I use them. For a while, I used expensive sable brushes for painting but am now primarily using the cheaper synthetic taklon brushes. Underglazes are hard on brushes and the sable seem to lose their point before the taklon. Most of the underglaze colors are mixable, though you often can't see what you're going to get.
For latex resist, I use temporary watercolor mask, usually Windsor and Newton. Latex resist destroys brushes, so I buy the cheapest plastic kiddie brushes from crafts stores, which cost about $.10 each. I use them once and toss them out. We don't have latex available for the Mudville students because I'm afraid all the studio brushes will get wrecked. I also use masking tape for resist when blocking out larger areas and bands around pots. Students use stickers, like hearts and dots, then peel them off and fill in with a second glaze application. I don't use latex resist on porcelain if I will be painting with underglazes. I find that the resist leaves behind a surface residue that blocks the absorption of some of the underglaze. This could be burned away by re-bisqueing but that's another step and more time. If I'm doing lines or other small areas, I often glaze the entire piece, then with a pointed tool, scrape back to the clay surface. Then I use damp Q-tips to clean up the clay before filling in the line or area with a contrasting glaze.
Wax resist is another way to isolate one glaze from another. I use wax resist when I've painted on top of a glaze and plan to dip the pot in another glaze. Latex is not suitable here because the latex will take off some of the underglaze color when it is removed the pot. Wax resist is easy to use over glazes except when you are using glazes with a dusty surface. I've heard of people spraying pots with spray starch (used in ironing clothes) to stabilize dusty glaze surfaces but my solution is to avoid glazes that are dusty.
I use a ceramic easel that I got more than 20 years ago, made by a company that became part of Scott Creek Pottery, the people who make excellent extruders. I don't believe that the easels are made anymore, a shame because the design is an excellent one. It would be very difficult for me to make some of the pots I make without the easel. It gives me a way to rest my hand away from the pot surface, helping to prevent smearing. Also, by supporting the pot, the easel makes work a lot less tiring and you don't have to worry about dropping the pot. A turntable raised to the right level (I use books) can also be very helpful and a substitute for an easel. Here are pictures and dimensions of the easel for anyone who wants to try to make his own.