I wouldn't say the Bush administration took measures to "prop up" the Soviet Union. Here's an answer I gave to a similar question a few months ago. To expand on it a bit, the Bush administration did not want the Soviet Union to collapse; they only want its hold on Eastern Europe to do so and, possibly, Soviet control over the Baltic states since the United States and many of its allies never recognized those states as a part of the Soviet Union.

A collapse of the Soviet Union had the high potential to lead to widespread violence among different ethnic groups and nationalities within the Soviet Union. To make matters much worse, an end to the Soviet Union meant its nuclear stockpiles would no longer be under control. Nuclear weapons could proliferate among the successor states raising the stakes of ethnic fighting and future crises. It was much more preferred that the Soviet Union continue to exist but undertake significant political and economic reforms to transform it into a market-oriented democracy. Since the start of the Cold War, U.S. policymakers had always believed that a democratic Soviet Union would not be a threat to the West. In the late 1980s and early 1990s, it appeared that such a Soviet Union was being born.

So the Bush administration, in conjunction with the West European nations, initiated a technical assistance program to aid Soviet officials in instituting these economic reforms. There were no official aid programs other than humanitarian assistance to feed, clothe, and shelter destitute Soviet citizens and some financial credits to support trade with the Soviet Union. These initiatives were originally launched in the lead up to and after the 1990 G7 Summit in Houston, Texas. A year later, the Soviet economic and political situation had only gotten substantially worse. As a result, the G7 at the 1991 London Summit reiterated its position from the previous year. At the end of the day, Bush wanted perestroika and reform to succeed but maintained that the Soviet people and leaders had to lead the way in transforming the Soviet system.

In addition to the sources listed on my other answer, I suggest reading the relevant parts of Jack F. Matlock, Jr., Autopsy on an Empire. New York: Random House, 1995. Matlock was the U.S. ambassador to the Soviet Union at the time.

I'm happy to answer any other questions on this topic. I actually just returned from a research trip at the Bush library last week to gather more primary sources on this topic in order to write the last chapter of my dissertation. I still have to review a lot of the material I gathered but I have a pretty good idea of what was and what was not on the table for U.S. policy options.