If redeeming KF for SQ, just do a search on SQ.com which is pretty straightforward. It gives 15% online booking discount and better availability. Only snag is sometimes you don't find availability for flights with same aircraft transit online (eg. SIN-SFO) but when you break them into separate segments (eg. SIN-HKG followed by HKG-SFO) you can see availability. If so, don't book online but call KF to book, and insist that they honour the 15% mileage discount.
If redeeming KF for *A, yes use the ANA tool. Simplest is to search by flight segment. No back tracking is allowed normally.