I use suitcase connectors.
View attachment 7319
The only soldering I've done so far is the feeder wires to the track. These connectors are made by 3M and other companies. 3M will always by 3 times the price "3 Multiplier" 3M. I got my from my store and we carry GARDNER BENDER INC MFG#10-2218 True Value(TV) SKU#553302. TV has 5pk and 25pk.
TV# 600497 MFG#10-100 25PK Tap Connector
25 Pack, Tap Splice CONNECTOR, Insulated, Solderless, 18-14 AWG, Clam. GARDNER BENDER INC
TV# 553302 MFG#10-2218 25PK Tap Connector
25 Pack, Tap Splice CONNECTOR, Insulated, Solderless, 22-18 AWG, Clam. GARDNER BENDER INC
TV# 599756 MFG#21-100 5PK Tap Connector
5 Pack, Tap Splice CONNECTOR, Insulated, Solderless, 18-14 AWG, Resealable Clam. GARDNER BENDER INC
TV# 553266 MFG#21-2218 5PK Tap Connector
5 Pack, Tap Splice CONNECTOR, Insulated, Solderless, 22-18 AWG, Resealable Clam. GARDNER BENDER INC
These are the descriptions off of the TV website.
Here is a video and at 1:40min. you can kinda see a few of them hooked up under the layout
Youtube video