I inherited from my father a Silex dowelling jig made in Australia which looks very similar to the #59 that Derek has shown us. These are frequently on ebay for minimal prices.
I also have found it to be very accurate and to make dowelling very easy and accurate.
I find dowelling with the Silex easy to do - but it is an alignment thing more than a strength thing- the real strength of the joint is the glue, not the dowel.
If it were done when 'tis done, then 'twere well it were done quickly