Permaset Aqua SuperCover is a line of opaque water base inks--white plus many other colors, so you don't need to underbase anything. It is made in Australia. I like to get it from these guys:
https://www.waterbaseinkusa.com/
But you can find it at a number of suppliers, just usually not in as wide a variety of sizes and colors and as good a price as at this place. It does cost more than most inks. Go figure.
The key to long term happiness with this ink is to replenish the moisture it loses to the screen and air with each use. I keep my working ink in a separate bucket so I always have fresh unmolested ink to compare to. Basically, if a big blob won't mostly slide off a metal spatula, it is too dry. One tends not to notice the gradual change from day to day, so it is easy to let it get too dry ... then all of a sudden you can't print worth poop and you can't figure out why

So best to add some water every time you put used ink back in the bucket.
I double-stroke this. Flood, Wet Stroke, Dry Stroke. Then flash and repeat as needed to get the level of "pop" you want.
Another option is Green Galaxy Comet White from Ryonet. It costs less, cleans up like it is a cleaner rather than an ink, is less prone to drying in the screen, and is generally easier to print than SuperCover. However, for a given number of hits, SuperCover would be brighter. Also it gets tacky/sticky when hot, so it really helps to have cooling station after your flash unit. It can also have a bit of a shine to it, and feels a bit more plasticky than SuperCover.
Pros and cons to every option. It's a matter of what's the best fit for you now.