I regularly transit the Brussels TMA at 80/90/100 IFR, with few issues. KOK BUB LNO NOR is standard. I haven't done it VFR for many years and don't know if there's an issue with it these days.
I've never used EDKB, but if you're going through the overhead, why not stop at EDGS, Siegerland? -- nice restaurant on field and, by reputation, a bit less hectic than KB, as well as being beyond the Cologne CTR. I wouldn't bet on EDKB to EDGS at 7500!