First thing I will say is that it's not the ghillie suit that makes the sniper hard to deal with, it's the player's fieldcraft. If the ghillie sniper can't do their role pretty much as effectively without the ghillie, then they need to take it off and practice their camo and concealment until they can do their job and have players almost tripping over without using the ghillie (if more people did this, they'd find they'd be waaaaaay more effective with the ghillie. It's like training with weighted clothing in DBZ ). Am I a jerk for thinking so? Maybe, but I also won't fault these players for playing how they want; that's what the hobby is all about, after all. I think the most important thing to say is prey upon their weaknesses. What I've found observing most bush wookiees in a counter sniper role is that they either move way too much or way too little. If they move too much, you see them and then it's just a case of suppressing them and advancing on their position to flush them out. If they move too little, you'll quickly be able to work out where they are and do the same, maybe with the help of smoke grenades or tag rounds. Also, if they're using a spring rifle, there's still usually a decent amount of noise unless they've really tuned it super well (which is rare), and also their bolt pull will be long, so look for that movement too. I would say to use their MED and slow ROF against them by moving and engaging their position with suppressive fire, but I've seen a lot of experienced bush wookiees moving away from bolties and toward 1J HPA setups as they still get the silence, but they get rid of the weaknesses of the bolt action platform. Personally, once I've cleared my debts, I'm shoving a Polarstar F2 into one of my m14s and relegating the VSR to a backup gun.
As a bush wookiee myself, I'll say the following for the majority of bush wookiees you'll be up against, in addition to the movement point above (most have already been said, but I figured I'd post up my views anyway):
Don't go to where your mate just got hit. The number of times I get multiple people because I hit someone and their friend either moves over to try and medic them immediately, or they move to take the cover their friend previously was. If they got hit behind that cover, it means someone has a line on it.
Move. Move. MOVE! Seriously, it's hard to hit shots on running targets and I'll usually just follow the target until they either move out of my line of sight, or they stop. This is harder if there are other players with AEGs around as they'll full auto your path and hit you, but if the sniper is being silly and being the hollywood "lone wolf" then if you keep moving you just won't get hit. BBs are about as consistent as a WE pistol in winter and the shot will go wide if there's a breeze or a leaf in the way, and trying to lead shots is difficult even in the best conditions (not impossible, but it makes the shot a lot harder).
Play the objective. Usually, snipers won't be holding the objective directly if it's like a base defense or something, because as a sniper you want to be where the enemy won't think you are. If there is a sniper in the base, then you know where they are and you just suppress them until you get close enough to hit them, which these days isn't much since hop ups are so good now that AEGs are shooting closer and closer to bolties. If the sniper isn't in the base and he hits you, don't go back to where you were attacking that time and instead push the objective from the other side. If the sniper is covering an objective like a flip can, think about where you got hit from and move to flank them instead. It's super hard to shoot someone behind you covertly when you're lying prone with a boltie, so you either have to let the flanking players pass (and probably take out a lot of your team) or you try and shoot them all super fast, which if there's more than one person you probably won't have much success.
If you know where the sniper is and they're not smart enough to have relocated, move around the position or fire and move to keep them suppressed as you close the gap. Most hides are awful when it comes to line of sight, because you need a bunch of stuff in the way for concealment. Usually, the sniper will only have one line that they're watching, so approach from their blind spot, or fire and move (quickly) to flush them out. It's hard to repel an attacking fire team with a boltie if they know where you are and are suppressing your position.
However, there are a few things that ghillie snipers will do to counter this. Some will carry a small AEG around with them, some will strike the right balance between moving too much or too little, some will run 1J HPA platforms for both silence and no MED. However, nobody is invincible without cheating. When dealing with a sniper, think about their limitations and the limitations of their current position and exploit what weaknesses you can.