CML,
Sorry for taking a while to get back to you, been putting in long hours in the shop. Lube squishing out of the patch isn't uncommon if the patches are well saturated with a more liquid lube. The weave of the patch does make a difference in how it will work in a given barrel. As Zimm said, going to a twill or flannel weave may work better because it's got more fluff. The material is more easily displaced from the area between the ball and rifling lands resulting in it compressing into the rifling grooves providing the gas seal - you're still getting a gas seal just in a different manner. Normally with a drill/duck type material, the patch material is not being displaced, it's being compressed with the higher compression happening between the ball and lands; in this situation, you're relying on the lesser area of compression between the ball and grooves being sufficient to seal the gas. They type of patching material used will definitely affect the way the load performs overall, not just the matter if you're getting a gas seal or not. I prefer starting with Dhaka muslin, it's quite versatile and generally works well in all calibers that are rifled or smoothbore. #2 drill will often suffice for 45 caliber and up smoothbore and barrels with standard depth rifling but will generally not work efficiently in deep rifling where it's often necessary to go with stressed duck or stressed raw (untreated) single-warp spun-weft Filson. 1/1 napped or unnapped twill for smoothbore or shallow groove of any caliber. 2/1 or 2/2 un-napped for deep groove in 45 caliber and up, napped for 45 caliber and under. It is very important that #1/#2 drill, Filson, duck and plain/sheeting weave fabrics be broken before use as patching, common pre-cut rounds & strips like CVA, T/C, Ox-Yoke, ect. are as-woven (un-broken) which is why one often needs to use excessive patch thickness to obtain an effective seal. Avoid any fabric that is unnaturally shiny, depending on how cotton is spun, it will have a natural sheen to it but if it's shiny, it's been treated with finishing agents that will often promote excessive fouling. On that same note, fabrics sold retail (in stores) are more often than not treated with sizing and finishing agents, both of which often cause fouling issues but more importantly they'll increase shot to shot deviation because of the varying friction factor between the patch and barrel.
I prefer raw Dhaka muslin cut at the muzzle. Getting a pre-cut round patch perfectly centered while loading is difficult and when the patch is too large as in using a 40-50 caliber patch in a 40 or 45 caliber, the excess flapped over the top of the ball often results in separation issues resulting in the ball being pushed off center of the bore by the patch as they separate. When done correctly, cutting at the muzzle eliminates excessive patch material issues - ball should be started only until it's flush or just slightly below flush with the muzzle, not more than 0.030".