I am trying to perform immunohistochemistry on cells which are growing in different wells of this kind of slide: https://www.fishersci.com/shop/products/hydrophobic-prntd-slide-8-well/5029205 (also attached an image in case the link changes)

I am having difficulty at the final mounting step when using Prolong Diamond. The normal method people seem to use, where you add a small amount of mountant to one side of the coverslip and let it creep across, fails to actually traverse the entire slide and the surface tension causes often causes the mounting media to hang at the edges of the wells, rather than actually filling them. It also ends up with a lot of void spaces where the mountant failed to cover the slide. To circumvent this, I've been using very large amounts of Prolong Diamond, but this causes a separate issue where the coverslip slides around easily during handling and large pools of mountant seep out the edges. This frequently results in cells being deformed/destroyed as I try to re-center the coverslip and press it down.

I've done trial runs with Vectashield Vibrance, which has the exact same issues, I suspect this is going to be a problem with any mountant with high glycerol percentages. Is there any mountant out there with lower viscosity that I can use? It would need to be compatible with DAPI, Alexafluor 488, and Alexafluor 555. Compatibility with Alexafluor 647 is also desirable, but not an absolute requirement.