Detailled instructions

sudo apt install curl jq -y

systemctl stop bitsong.service

# Always backup priv_validator_state.json on validator node, to avoid double-sign
cp $HOME/.bitsongd/data/priv_validator_state.json $HOME/.bitsongd/priv_validator_state.json.backup

If possible, keep this backup until your node is running
mv $HOME/.bitsongd/data $HOME/.bitsongd/data.backup

mkdir $HOME/.bitsongd/data
cp $HOME/.bitsongd/priv_validator_state.json.backup $HOME/.bitsongd/data/priv_validator_state.json

RPC1=https://bitsong-rpc.bluestake.net:443
RPC2=https://rpc.cosmos.directory:443/bitsong

LATEST_HEIGHT=$(curl -s $RPC1/block | jq -r .result.block.header.height); \
BLOCK_HEIGHT=$((LATEST_HEIGHT - 2000)); \
TRUST_HASH=$(curl -s "$RPC1/block?height=$BLOCK_HEIGHT" | jq -r .result.block_id.hash)

sed -i.bak -E "s|^(enable[[:space:]]+=[[:space:]]+).*$|\1true| ; \
s|^(rpc_servers[[:space:]]+=[[:space:]]+).*$|\1\"$RPC1,$RPC2\"| ; \
s|^(trust_height[[:space:]]+=[[:space:]]+).*$|\1$BLOCK_HEIGHT| ; \
s|^(trust_hash[[:space:]]+=[[:space:]]+).*$|\1\"$TRUST_HASH\"|" $HOME/.bitsongd/config/config.toml

systemctl start bitsong.service

journalctl -u bitsong

# Is your node catching up?
curl http://localhost:26657/status | jq .result.sync_info