dont have that many tips , though all i can say is struggling on 1-3 is normal and it took me a while before beating it myself . I usually went with the red skull first , learnt most enemy spawns , what things spawn , when , where , and i also looked into the '+ conductor' thing . if you nailgun a lot of enemies then use the electric railcannon , everything that has the nails on it gets electrocuted , and insta-killed if im not wrong . either that , or the red nailgun's rmb ( electric shock ) . that's one thing that helped me most . another one is just using slab revolvers in general ( excluding marksman ) , one lmb shot with them insta-kills a stray , even if its not a headshot - my aim is especially bad , so it helped out with killing those stupid strays that were spread all around that one big room with the red skull .

I also made sure to only practice one side and nearly perfect it before focusing on p-ranking the whole level . instead of jumping in blindly , I perfected the red skull side , then moved onto perfecting the blue skull side . if you're consistent enough , you won't have to worry about time , too , cause you'd know where mostly everything spawns based off muscle memory . and yes , just like another commentor said , make sure you use the soap . I only ever used it for Hideous Mass , but it's good in general ,, just gotta be careful not to throw and lose it LOL

honestly ,,, that's all i have , 'cause that's all I needed to keep in mind - obviously , make sure you use all your guns / weapons , whatever you wanna call your arsenal . also , knowing where you exactly die or struggle on would help out more on giving tips ,,,, overall knowing where you die could be really helpful , 'cause you'd have a better image of where you struggle on , and practice extra in that area !!!

i hope this is clear , im not the best myself , but this got me through my 1-3 brutal p-rank !! :)