I used to use a 50-50 mixture of green soap and hydrogen
peroxide. Both are available at any drug store. The green soap
is a liquid. Get the smallest amount you can get. Paint it on
the models, rinse and let it dry. Problems arise when people
have water drops on the model when investing. It dilutes the
investment around the model and they get strange textures.
The new waxes don’t seem to be helped by this step. The
commercial models also seem to not need this de-bubbler