Sorry on delay. New baby girl & Farm stuff eating up all my spare time.
I still use the tip that came with it. Adjustable and I've not had problems BUT maybe I don't know what I'm missing?? I could have changed a nozzle a while ago and forgot though too, so, I guess I'm saying, dunno on that one, experiment and see which you like best.
WARM SEASON - you will kill those with NOTHING RIGHT NOW.... not round-up, not clethodim, not oust, nothing. You need to wait until the natives are up and growing quite well (yes, there's growth stages they are most vulnerable to kill but just wait until you have maybe 12" of growth for example and you'll kill em fine.). So, natives are likely still dormant now. I'm going to guess, depending on soil temperatures, you'll see growth in a month and 6-8 weeks you can do your spraying for example. You will 100% want to use clethodim & crop oil and I'd use them at high rates. Round-up is out of the question unless you're a precision expert on not getting any drift on trees (don't try it, just use clethodim & Crop oil). This will kill cool seasons and warm seasons.
if you're talking "IDEAL KILLING TIME" which we almost never can do things "perfect" - we all have to compromise..... Your best killing time on brome & Fescue & cool seasons is generally May 20th. Before reproduction of plant starts. On Warm seasons, generally a month or 6 weeks later. BUT - realistically..... especially if you're not covered solid in warm seasons.... I'd just spray it all around May 20-30th. It SHOULD get natives if you spray heavy enough. Like, I'd suggest 20-25 OZ or even 30 of Clethodim and then the crop oil & at least 2 residual herbicides, 3 would be better. What you will see if natives aren't all killed- you'll see some nice looking sparse Native clusters here and there BUT again, unless it's crazy thick native stand, it really isn't going to hurt anything having a small amount of natives that didn't die among your trees. Good luck!