Through the creation of an instant Glitch City it is possible to create a suitable Glitch City for "-" move corruption or LOL glitch in order to obtain specific Pokémon and/or glitch Pokémon, and this can be achieved simply by modifying items in the expanded items pack.
Instant Glitch City
By modifying the quantity of item 33 and the identifier of item 34 (address D35F-D360 in Red/Blue or D35E-D35F in Yellow) in the expanded items pack, the player can create a Glitch City that is seen from the start menu after the Trainer card is viewed but not when the start menu is closed.
Regardless, they can still be used for buffer overflow techniques, such as specific "-" move corruption, LOL glitch or Super Glitch corruptions and notably oobLG in a map with a PC.
The y-block address (Red/Blue D363; item 35 quantity) and x-block address (Red/Blue D364; item 36) as well as the map's width (D369; item 38's quantity), as well as the original map number (D35E; item 33's quantity) if the player is getting the Glitch City from banked ROM (0x4000-0x7FFF) will also control how the Glitch City appears on the map.
Although usually these are not displayed when the start menu is closed, the map can be applied when the start menu is closed through the use of the 9Fglitch item in Yellow or a custom map script/arbitrary code execution in Red and Blue. One way to do it in Red and Blue is to place an X Attack x18 into item 41.
The Pokémon speedrunning community created instant LOL glitch/CoolTrainer logs for obtaining most Pokémon and glitch Pokémon with specifics relating to the map data needed. These may be found here in the instaCT logs.zip folder.
Notably the following Pokémon and glitch Pokémon in Red and Blue cannot be obtained with instant LOL glitch/CoolTrainer or RAM LOL glitch/CoolTrainer alone (at least for ROM locations but possibly from anywhere), which may be due to the lack of an appropriate map block containing the index number of the Pokémon at the right place.