The agent you have is just performing Matrix Perception and checking your deck for marks, right? 'Cause that's the easiest way and it's not an opposed test.
Also, talk with your GM to get a good understanding how they're handling Matrix Perception. I say this because the rules are very vague about what you need to know to find something that is hidden or over 100m away. A good example is the beginning of Splintered States, where you are tasked to find a commlink. If your GM says you have enough information to find it with a Matrix Perception test, then that can really change the story from happening how it's intended to. Especially in combat, you need to make sure you both agree on what you need to know if you want to start finding devices your opponents are using or locating an enemy decker's cyberdeck.
I also second DeathEatsCurry's suggestion to have Configurator set to a full cybercombat loadout, with max Attack, low Sleaze, and then Hammer, Exploit, and either Fork or Mugger. Personally I prefer Fork, because with 7 Attack and a +2 from Exploit, that's generally enough to brick most basic devices like cyberware and smartguns assuming you get a net hit or two and it can be done much faster than trying to mark them first. In my personal experience, combat goes by too quickly for you to do a lot of marking or other actions.
Remember that your character's strength is also in information and logistics. Sharing video feeds, using AROs to mark targets, letting your allies know if you find a number of smart weapons on the enemy... You can even find otherwise hidden enemies. An assassin might be stealthier, physically, but unless they also have a very high-end cyberdeck, their equipment will be rolling just LOG or Device Rating to stay hidden when running silent. If something's within 100m of you and visible to you in AR, the ARO you put on it (that you can decide is only visible to you and your team) can be used to find them without needing a Trace Icon action, or so is my understanding.
Also, though you're no rigger, drones can be your friend as well. One spying drone can be useful to help you locate potential targets and cameras. Especially if you have a high Electronic Warfare skill and try using the sensor array available in drones to find things. Along this same line, if you have a cyberarm, putting a sensor array in it can give you access to a lot of information you can gain rather subtly, like using a cyberware scanner or MAD scanner on someone you're talking with without them knowing. Also, an ultrasound scanner can be used to essentially create 3D maps of an environment.
