Percentage solutions in a lab are typically expressed as weight-to-volume percentages. So you'd want 50 grams of NaOH dissolved in 1 Liter of water to make a 5 w/v% solution. That strength will work. I'd recommend dividing your solution in half. Soak the anion exchange resin in 1/2 of the solution in a glass container (wide-mouth mason jars work well for this purpose) for an hour. Pour off the solution (you can pour it down the drain, which will have the added bonus of clearing any clogs), rinse it with one rinse of RODI, soak the resin again in the second half of the solution for another hour, pour it off, rinse well with RODI (cover the resin with RODI, let it set for 15 minutes, pour it off, repeat 3 times).
When done, you can remove the excess liquid by scooping the resin out on a paper towel. But don't let it dry, which will crack the resin particles. If you want to store the resin for some period of time, seal it in a mason jar while it's still damp, and store it in the refrigerator (which prevents mold).
