You could have a look at rodeoh style harnesses...
you could have a look at strapless strapons... some people use them with panties, or a harness...
use safe silicone, or a condom... some materials are not that safe...
if using a harness, there are devices that also please the wearer... or strapless strapons, there are some with ridges to please the wearer...
concerning anal, you might try not too big ones first...
and there are bent dildos available, so they can reach certain spots better which can be very pleasurable...
one is the p/g-spot, towards the stomach..
which can be very pleasurable anally stimulated both for ftm and mtf people...
and you might try different motions...
deeply pressed... slow pressed...a bit faster... etc
use enough organic lube, and take it slow in the beginning...
you might tell them to relax... there is a muscle in the anus which should be relaxed for better entry...
all at your own risk (use common sense with panties and strapless strapons for example... not too small panties etc)

hugs