I haven't any CRP, but I have planted trees/shrubs for 3 springs: 500 bareroots first year -> 625 second year -> 300 third year ... probably some more this year.
What's worked best for me is a backpack sprayer with RU and a piece of 180 degree piece of ducting on an old hockey stick shaft that I use to guard the shrubs as I spray. I have a 4 gallon sprayer, but that doesn't mean you need to fill up all the way up. I find 3 gallons a good compromise between weight and duration between fill-ups. I spray 2-3 times per year depending on growth and temperature. During the heat of summer I sometimes like to leave some weed growth around the base - keeps the shrub partially shaded and keep the dirt from really drying out; both helping to conserve moisture!
The hardest part is finding non-windy days to spray. Wind drift can screw things up a bit if you've planted things too close together. On a calm day the plants set 1'-2' apart are still hard, but most are 4'-5' spacing.
Even if you accidently hit a shrub, if you have mixed the RU properly, most shrubs are just set back, but don't die. Occasionally if I see I sprayed the edge of one, I'll just rip the small part that got sprayed completely off to keep the plant from absorbing the RU.