You do not say what the bushing is and what material you are inserting it into.
You could try warming the surrounding structure and putting the bushings in dry ice.
If these are aircraft parts you are going to have to be careful with heat treat temperatures.
B.E.
Since you specified a "shrink" fit, I'll assume you mean thermal fit. There are no proprietary tools or processes required to perform thermal fitting of a bushing into a bore. You just need to machine the bushing OD and bore to the correct diameters, heat the bore and/or cool the bushing enough to permit a slip fit, and then push the bushing into place. You may want to make a simple press tool that pilots on the bushing ID and has a shoulder to make sure that the bushing goes in square and is installed at the appropriate height in the bore.
Depending upon the degree of interference in your bushing's fit and the relative stiffness of the bushing and housing, the bushing bore may require boring and/or honing after installation to correct the bore size and shape.
when the bushing hits the heated parts there is instantaneous thermal transfer of the heat upon the
bushing. it is done on aerospace & aircraft parts.
the parts are heated 50 deg below the tempering temperature.
the bushing are normally dipped in liquid nitrogen - 300 deg F approx. "to obtain maximum contraction of the bushing"
once the parts are mated the heat from the larger mass will over take the bushing.
tooling is generally required because the assembly must be very quick.
I have assembled pins , gear shafts & so on this way.
I could not write a process spec that was titled "Shrink Fit Bushing Install Method" and have the spec say nothing but "use a torch and a bucket of dry ice."
Recommend freezing the bushing on dri-ice [covered with insulation] for at least 30-minutes. Remove the bushing with tongs [wood preferred] or protective gloves and install [press] in hole within ~15--20 seconds. Note: to facilitate installation and improve corrosion resistance, may apply wet-sealant or epoxy primer to hole [bore] just before bushing installation. Fillet around both ends with "squeze-out" [wipe-away excess].
