Exactly the same as the initial photoresist method used for the traces. I use another sheet of photoresist (from Digole).
Print the pad/cream layers from eagle along with any text you want to show on board. Expose and develop, then bake in the over/toaster on 200F for 10 minutes (or so...). Don't quote me on the temp/time, I read it online and it seems to work. If all the text resides over a copper plane, then simply tinning it with LiquidTin will make the text very readable. If not, you can use a WHITE crayon and hot-air gun/hair dryer to melt wax into the text depressions. Colors don't seem to work very well for me.
I have NO idea what chemicals/fumes this releases in the oven, so you may not want to use your main appliances for it without a little more research.
For a thicker solder mask, you could use 2 layers of photoresist (removing protective films in between) and expose for somewhat longer than usual. (I've only used one layer, so i don't know how well that works)
--- In Homebrew_PCBs@yahoogroups.com, Shannon Haworth <shannon.haworth@...> wrote:
>
> What technique did you use to prepare the solder mask?
>
> Shannon