Annie,

It is possible to make very good enlarged negatives from transparencies (and from Scala) but it is hard to be specific about development times wiithout doing the work because the requirments are quite different from normal devlopment of negatives. You want a film that has a very straight line curve and both TMAX 100 and 400 satisfy that requirment very well.

Film has a lot more sensitivity than mateials we normally work with in the darkroom so you want to make sure there are no light leaks in your room. Cover your enlarge with a piece of black cloth or a black bag because it is almost certain to leak a little light. Your exposures will be quite short, even with the lens stopped down, so you probably need a digital timer.

In general film needs to be developed about 50% longer for Pt/Pd printing than for regular silver gelatin work, but in this case since you are starting with a transparency there is no reference. But when you look at the negative it should appear to have a lot more contrast than your regular negatives.

You should be able to enlarge your slides between 6-10X without getting too much grain. Of course, this will depend on the grain in your slides and on your individual tolerance of grain.